tag:theconversation.com,2011:/ca/topics/chemical-elements-28289/articlesChemical elements – The Conversation2021-06-02T14:27:04Ztag:theconversation.com,2011:article/1619342021-06-02T14:27:04Z2021-06-02T14:27:04ZGeometrically baffling ‘quasicrystals’ found in the debris of the first-ever nuclear blast<figure><img src="https://images.theconversation.com/files/404021/original/file-20210602-23-j7l21n.jpeg?ixlib=rb-1.1.0&rect=7%2C7%2C1614%2C945&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The heat and pressure generated by a nuclear explosion can produce unusual chemical curiosities. </span> <span class="attribution"><a class="source" href="https://upload.wikimedia.org/wikipedia/commons/f/fc/Trinity_Detonation_T%26B.jpg">United States Department of Energy/wikimedia</a></span></figcaption></figure><p>Nuclear detonations unleash an astonishing amount of destructive force. But the extreme <a href="https://www.sciencedirect.com/science/article/pii/B012227410500315X">pressure</a> and <a href="https://www.sciencedirect.com/book/9780128013007/materials-under-extreme-conditions">temperature</a> that they generate also makes nuclear blasts a cauldron of chemical creation, capable of delivering new and surprising scientific discoveries.</p>
<p>In the 1950s, for instance, scientists examining debris from US <a href="https://time.com/4096424/ivy-mike-history/">hydrogen bomb tests</a> found two new elements, which now occupy numbers 99 and 100 in the periodic table. They named them after prominent nuclear scientists: <a href="https://theconversation.com/einsteinium-100-years-after-einsteins-nobel-prize-researchers-reveal-chemical-secrets-of-element-that-bears-his-name-154447">einsteinium</a> for Albert Einstein, and <a href="https://www.britannica.com/science/fermium">fermium</a> for Enrico Fermi.</p>
<p>Now, scientists sifting through debris at the site of the <a href="https://theconversation.com/this-is-what-happened-the-morning-the-first-atomic-bomb-created-a-new-world-142184">first-ever nuclear bomb detonation</a> – held in New Mexico in July 1945 and named <a href="https://www.atomicheritage.org/history/trinity-test-1945">the Trinity test</a> – have unearthed a different chemical oddity. <a href="https://www.pnas.org/content/118/22/e2101350118">In their paper</a>, the researchers report the discovery of a previously unknown type of “<a href="https://www.britannica.com/science/quasicrystal">quasicrystal</a>” – a crystal formation once thought impossible due to its irregular geometric structure.</p>
<h2>What are quasicrystals?</h2>
<p>Quasicrystals were <a href="https://journals.aps.org/prl/pdf/10.1103/PhysRevLett.53.1951">first discovered</a> by material scientist Dan Schechtman in 1984, but were initially seen as highly controversial – even impossible – because their unique form is not allowed by the rules defining crystal structures.</p>
<p>Crystals are composed of units that repeat periodically in three dimensions. A good way to think of this is to picture them in two dimensions. You can tile a floor with certain geometric shapes – like squares, triangles and hexagons – because they tessellate, meaning that they can be slotted together in a repeating pattern with no overlaps or gaps. You can’t do this with pentagonal or heptagonal tiles. They can’t be tessellated, so they’d leave irregular gaps on your floor.</p>
<p>Three dimensional crystal structures adhere to the same rule. The repeating units naturally arrange themselves in a regular pattern – filling up all the available space. A <a href="https://www.sciencedirect.com/topics/chemistry/simple-hexagonal-crystal-system">hexagonal arrangement</a>, for instance, is a typical crystal structure.</p>
<figure class="align-center ">
<img alt="A hexagonal pattern of bonded spheres" src="https://images.theconversation.com/files/404044/original/file-20210602-25-6j3u08.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/404044/original/file-20210602-25-6j3u08.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/404044/original/file-20210602-25-6j3u08.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/404044/original/file-20210602-25-6j3u08.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/404044/original/file-20210602-25-6j3u08.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/404044/original/file-20210602-25-6j3u08.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/404044/original/file-20210602-25-6j3u08.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Crystals of ice arrange to form a hexagonal structure.</span>
<span class="attribution"><a class="source" href="https://upload.wikimedia.org/wikipedia/commons/8/88/Ice_XI_View_along_c_axis.png">Danski14/wikimedia</a></span>
</figcaption>
</figure>
<p>The general rule is that crystals must have repeating units with 2-fold, 3-fold, 4-fold or 6-fold axes. Here, “fold” means how many times you can rotate the three-dimensional crystal unit so that it looks the same as its starting position – enabling tessellation. The rule means that crystal units with a 5-fold axis (pentagonal) or anything 7-fold and above (heptagonal and beyond) won’t tessellate, and therefore cannot exist.</p>
<h2>Penrose tiling</h2>
<p>This rule held until 1974, when the British mathematical physicist Roger Penrose found a way to cover a two dimensional space like a floor with shapes that <a href="https://link.springer.com/article/10.1007/s11224-020-01669-8">do not repeat periodically</a> – a form of tessellation now called “<a href="https://www.maths.ox.ac.uk/node/865">Penrose tiling</a>”.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/yxlEojkVJ0c?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Penrose tiling uses just two shapes: a kite and a dart.</span></figcaption>
</figure>
<p>These ideas were soon applied to <a href="https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.53.2477">three-dimensional structures</a>, and it was in 1984 that Schechtman published his experimental work on quasicrystals. His discovery won him the <a href="https://www.nobelprize.org/prizes/chemistry/2011/shechtman/facts/">Nobel Prize for Chemistry in 2011</a>. </p>
<p>Over 100 types of quasicrystal have been discovered since, though nearly all of them have been produced in the lab. <a href="https://www.newscientist.com/article/2115570-third-ever-natural-quasicrystal-found-in-siberian-meteorite/">Three exceptions</a>, found <a href="https://www.pnas.org/content/109/5/1396">within the Khatyrka meteorite</a> in north-eastern Russia, may date back to the beginning of our solar system. And now there’s another, which is the oldest existing quasicrystal to have been produced – albeit accidentally – as a result of human activity.</p>
<h2>New quasicrystal</h2>
<p>The new quasicrystal was found within a glassy material called red trinitite, which the scientists sourced from the site of the 1945 nuclear blast. The trinitite was formed at the moment of the Trinity test’s detonation, when the desert sands of New Mexico were thrown up into the air and heated to 8,000°C before raining down as newly synthesised trinitite.</p>
<p>This new quasicrystal is <a href="https://math.wikia.org/wiki/Icosahedron">icosahedral</a> – possessing 20 faces – and is structured with 2-fold, 3-fold and 5-fold symmetry axes. This means that there are three specific perspectives of this complex 3D structure that are repeated identically when it’s rotated: one is repeated twice, one three times, and the other five times. It’s the 5-fold axis – like the two dimensional pentagon we know can’t tessellate – that means the sample is a quasicrystal.</p>
<p>It’s also a unique sample, because the quasicrystal has silicon, calcium and copper in its composition. The copper, which gives the trinitite its red hue, is likely to have found its way into the quasicrystal via a set of transmission lines that ran close to the site of the bomb test and were vaporised along with the sand upon detonation.</p>
<h2>Learning from quasicrystals</h2>
<p>Practically, material scientists are exploring the <a href="http://mcs.open.ac.uk/ugg2/quasi_intro6.shtml">application of quasicrystals</a> to exploit their poor heat conductivity, which is possibly related to their non-periodic structures. They’ve already been used as coatings in <a href="https://www.nature.com/articles/d41586-019-00026-y">non-stick frying pans</a>, for example. Other suggested applications include <a href="https://phys.org/news/2020-09-scientists-capture-polymeric-quasicrystal.html">LED lights</a> and surgical instruments, but their development is at an early stage. </p>
<p>But if more of these crystallographic and chemical curiosities are found in the debris left behind by nuclear bomb tests, studying their composition could also help scientists understand the ferocious forces at play in the heart of nuclear blasts – a place no scientific instrument has yet measured directly.</p><img src="https://counter.theconversation.com/content/161934/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Robert A Jackson does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The quasicrystals were ‘accidentally’ synthesised during the first test of a nuclear bomb in July 1945.Robert A Jackson, Reader, School of Chemical and Physical Sciences, Keele UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1544472021-02-03T16:09:57Z2021-02-03T16:09:57ZEinsteinium: 100 years after Einstein’s Nobel Prize, researchers reveal chemical secrets of element that bears his name<figure><img src="https://images.theconversation.com/files/382226/original/file-20210203-21-6vkxsw.jpg?ixlib=rb-1.1.0&rect=42%2C26%2C938%2C683&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Albert Einstein photographed on a trip to America in the wake of his Nobel prize-winning discoveries.</span> <span class="attribution"><a class="source" href="https://picryl.com/media/albert-einstein-washington-dc">Harris & Ewing/PICRYL</a></span></figcaption></figure><p>A century ago, an upstart German physicist by the name of Albert Einstein turned the scientific world on its head with his discovery of the photoelectric effect, which proved light to be both a particle and a wave. <a href="https://www.nobelprize.org/prizes/physics/1921/einstein/facts/">Awarded the</a> 1921 Nobel prize in physics for his work, Einstein would later contribute to theories related to nuclear fusion and fission – arguably paving the way for the invention and detonation of nuclear weapons, as well as nuclear energy.</p>
<p>And so, when elements previously unknown to science were discovered in the chemical debris of a nuclear explosion 69 years ago, it was fitting that scientists named what they found after the great physicist – adding “<a href="https://www.rsc.org/periodic-table/element/99/einsteinium">einsteinium</a>” to the periodic table. </p>
<p>Now, 100 years after Einstein’s Nobel prize win, chemists have finally been able to peer into the chemical behaviour of this elusive, highly radioactive element. What they’ve learned could help scientists further expand our understanding of the periodic table – including elements that are yet to be added to it.</p>
<h2>Explosive findings</h2>
<figure class="align-right ">
<img alt="A blue glowing vial of a chemical" src="https://images.theconversation.com/files/382276/original/file-20210203-15-1jxhhxv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/382276/original/file-20210203-15-1jxhhxv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=867&fit=crop&dpr=1 600w, https://images.theconversation.com/files/382276/original/file-20210203-15-1jxhhxv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=867&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/382276/original/file-20210203-15-1jxhhxv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=867&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/382276/original/file-20210203-15-1jxhhxv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1090&fit=crop&dpr=1 754w, https://images.theconversation.com/files/382276/original/file-20210203-15-1jxhhxv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1090&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/382276/original/file-20210203-15-1jxhhxv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1090&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">300 micrograms of einsteinium.</span>
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<p>Einsteinium (Es) is the 99th element in the periodic table. It was first discovered in 1952 when a thermonuclear device dubbed “Ivy Mike” was detonated on the island of Elugelab in the Pacific Ocean (now part of the Marshall Islands). Ivy Mike’s detonation was the first demonstration of a hydrogen bomb. Such a blast creates four times more energy than nuclear fission bombs (like those dropped on Japan in 1945) and four million times more energy than the burning of a similar amount of coal.</p>
<p>It was in the fallout from Ivy Mike’s explosion, amid the chemical debris, that atomic number 99 was found for the first time. Only about 200 atoms of this element were detected, which shows just how scarce it is. It took nine years of painstaking work for scientists to be able to synthesise element 99 in a lab, <a href="https://link.springer.com/chapter/10.1007%2F1-4020-3598-5_12">which they achieved in 1961</a>.</p>
<p>The team of researchers who made the discovery thought about naming the element “pandamonium”, since the project team behind Ivy Mike had operated under the acronym “PANDA”. But in the end, they decided to honour Albert Einstein. </p>
<figure class="align-center ">
<img alt="A large mushroom cloud captured on old film cameras" src="https://images.theconversation.com/files/382203/original/file-20210203-17-1481lh9.jpg?ixlib=rb-1.1.0&rect=4%2C8%2C2849%2C2229&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/382203/original/file-20210203-17-1481lh9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=471&fit=crop&dpr=1 600w, https://images.theconversation.com/files/382203/original/file-20210203-17-1481lh9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=471&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/382203/original/file-20210203-17-1481lh9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=471&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/382203/original/file-20210203-17-1481lh9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=591&fit=crop&dpr=1 754w, https://images.theconversation.com/files/382203/original/file-20210203-17-1481lh9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=591&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/382203/original/file-20210203-17-1481lh9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=591&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">The blast from the Ivy Mike atmospheric nuclear test, photographed on November 1 1952.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/w/index.php?curid=19280560">The Official CTBTO Photostream/Wikimedia</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
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<h2>Too hot to handle</h2>
<p>Perhaps unsurprisingly, very little has been known about einsteinium. An element birthed in a thermonuclear blast, it’s incredibly hard to experiment with due to its extreme radioactivity. Not only is it literally too hot to handle – one gram of einsteinium produces 1,000 watts of energy – it also emits harmful gamma rays, so working with the element requires researchers to wear protective gear at all times.</p>
<p>What’s more, einsteinium’s most commonly occurring form (called Es-253, based on the number of neutrons in the atom’s nucleus) has a <a href="https://www.radioactivity.eu.com/site/pages/Radioactive_Half_life.htm">half-life</a> of only 20 days. That means that, after 20 days, einsteinium decays by half. After a couple of months, the tiny quantities of the element that scientists are able to work with practically disappear.</p>
<p>So it’s no wonder that it’s taken nearly 70 years for scientists to get to grips with this element. But now, a team from the Lawrence Berkeley National Laboratory and the University of California at Berkeley have managed to pin down enough einsteinium to run some basic tests on the element – breaking new ground in experimental chemistry and fundamental science.</p>
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Read more:
<a href="https://theconversation.com/five-chemistry-inventions-that-enabled-the-modern-world-42452">Five chemistry inventions that enabled the modern world</a>
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<p>In <a href="https://www.nature.com/articles/s41586-020-03179-3">their paper</a>, the researchers explain how they managed to use just 200 nanograms of Es-254 (a rare form of einsteinium with a half-life of 275.5 days) to run their experiments. A nanogram is just one billionth of a gram, so these experiments took place on an incredibly small scale.</p>
<h2>Einsteinium chemistry</h2>
<p>Performing chemistry with einsteinium for the first time, the research team managed to synthesise a chemical compound that included the element in order to examine how it might interact with other elements in a compound. This was done under the <a href="https://www-ssrl.slac.stanford.edu/">Stanford Synchrotron Radiation Lightsource</a>, which beams high-energy light at chemical compounds to enable their structure to be exposed. You can think of this method as similar to how silhouettes are formed – but on an atomic scale.</p>
<p>One big finding was the bond distances between einsteinium atoms and other atoms around it – like carbon, oxygen and nitrogen. Knowing einsteinium’s bond distances for the first time means we can predict what other combinations of compounds featuring einsteinium will look like – adding entirely new combinations to our current knowledge of chemistry. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/382255/original/file-20210203-15-c6cu1m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="The periodic table, in colour" src="https://images.theconversation.com/files/382255/original/file-20210203-15-c6cu1m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/382255/original/file-20210203-15-c6cu1m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=385&fit=crop&dpr=1 600w, https://images.theconversation.com/files/382255/original/file-20210203-15-c6cu1m.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=385&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/382255/original/file-20210203-15-c6cu1m.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=385&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/382255/original/file-20210203-15-c6cu1m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=484&fit=crop&dpr=1 754w, https://images.theconversation.com/files/382255/original/file-20210203-15-c6cu1m.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=484&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/382255/original/file-20210203-15-c6cu1m.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=484&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">The periodic table. Einsteinium features on the bottom row under ‘Es’.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-vector/periodic-table-elements-colorful-vector-illustration-786893179">Humdan/Shutterstock</a></span>
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<p>Crucially, the researchers also managed to determine the valence state of einsteinium. An atom’s valence controls how many other atoms it can bond to. This quantity is of fundamental importance in chemistry, determining the shape and size of the building blocks from which the universe is made. Einsteinium also happens to lie at an ambiguous position on the periodic table, between elements with different valences, so establishing its valence was also important for understanding its position in the table. </p>
<p>Einsteinium is currently the heaviest chemical element that can be examined in this way – so it’s exciting for chemists that new ground has been broken by this recent paper. The challenge facing future chemists is to try to synthesise heavier elements in similarly measurable quantities, revealing more about the chemicals that make up our world.</p>
<p><em>This article was amended on February 17, 2021 to clarify the definition of valence and to make clear that einsteinium’s valence helps us understand, not organise, its position in the periodic table.</em></p><img src="https://counter.theconversation.com/content/154447/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Robert A Jackson does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The element was discovered in the fallout of a thermonuclear blast.Robert A Jackson, Reader, School of Chemical and Physical Sciences, Keele UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1439792020-08-05T04:46:47Z2020-08-05T04:46:47ZWhat is ammonium nitrate, the chemical that exploded in Beirut?<p>The Lebanese capital Beirut <a href="https://www.theguardian.com/world/live/2020/aug/04/beirut-explosion-huge-blast-port-lebanon-capital">was rocked</a> on Tuesday evening local time by an explosion that has killed at least 78 people and injured thousands more.</p>
<p>The country’s prime minister Hassan Diab said the blast was caused by around 2,700 tonnes of ammonium nitrate stored near the city’s cargo port. Video footage appears to show a <a href="https://www.npr.org/2020/08/04/898969935/massive-explosion-rocks-beirut-damaging-buildings-and-shattering-windows">fire</a> burning nearby before the blast. </p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1290672351844196352"}"></div></p>
<p>Ammonium nitrate has the chemical formula NH₄NO₃. Produced as small porous pellets, or “prills”, it’s one of the world’s most widely used fertilisers. </p>
<p>It is also the main component in many types of mining explosives, where it’s mixed with fuel oil and detonated by an explosive charge.</p>
<p>For an industrial ammonium nitrate disaster to occur, a lot needs to go wrong. Tragically, this seems to have been the case in Beirut. </p>
<h2>What could have caused the explosion?</h2>
<p>Ammonium nitrate does not burn on its own. </p>
<p>Instead, it acts as a source of oxygen that can accelerate the <a href="https://www.bbc.co.uk/bitesize/topics/zypsgk7/articles/zcwxcj6">combustion</a> (burning) of other materials. </p>
<p>For combustion to occur, oxygen must be present. Ammonium nitrate prills provide a much more concentrated supply of oxygen than the air around us. This is why it is effective in mining explosives, where it’s mixed with oil and other fuels.</p>
<p>At high enough temperatures, however, ammonium nitrate can violently decompose on its own. This process creates gases including nitrogen oxides and water vapour. It is this rapid release of gases that causes an explosion. </p>
<p>Ammonium nitrate decomposition can be set off if an explosion occurs where it’s stored, if there is an intense fire nearby. The latter is what happened in the 2015 <a href="https://www.bbc.com/news/world-asia-china-37927158">Tianjin explosion</a>, which killed 173 people after flammable chemicals and ammonium nitrate were stored together at a chemicals factory in eastern China.</p>
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Read more:
<a href="https://theconversation.com/explainer-how-dangerous-is-the-sodium-cyanide-found-at-tianjin-explosion-site-46229">Explainer: how dangerous is the sodium cyanide found at Tianjin explosion site?</a>
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<p>While we don’t know for sure what caused the explosion in Beirut, footage of the incident indicates it may have been set off by a fire – visible in a section of the city’s port area before the explosion happened. </p>
<p>It’s relatively difficult for a fire to trigger an ammonium nitrate explosion. The fire would need to be sustained and confined within the same area as the ammonium nitrate prills. </p>
<p>Also, the prills themselves are not fuel for the fire, so they would need to be contaminated with, or packaged in, some other combustible material.</p>
<h2>Residents’ health at risk</h2>
<p>In Beirut, it has been reported 2,700 tonnes of ammonium nitrate were <a href="https://www.theguardian.com/world/live/2020/aug/04/beirut-explosion-huge-blast-port-lebanon-capital">stored in a warehouse</a> for six years without proper safety controls.</p>
<p>This will almost certainly have contributed to the tragic circumstances that resulted in a commonplace industrial fire causing such a devastating explosion.</p>
<p>An ammonium nitrate explosion produces massive amounts of <a href="https://www.abc.net.au/news/2020-06-15/bright-orange-mine-blast-concerns-residents/12332224">nitrogen oxides</a>. Nitrogen dioxide (NO₂) is a red, bad-smelling <a href="https://www.abc.net.au/news/2020-06-15/bright-orange-mine-blast-concerns-residents/12332224">gas</a>. Images from Beirut reveal a distinct reddish colour to the plume of gases from the blast. </p>
<p>Nitrogen oxides are commonly present in urban air pollution, and can irritate the respiratory system. Elevated levels of these pollutants are particularly concerning for people with respiratory conditions.</p>
<p>The fumes in Beirut will present a health risk to residents until they naturally dissipate, which could take several days depending on the local weather. </p>
<h2>An important reminder</h2>
<p>Here in Australia, we produce and import large amounts of ammonium nitrate, mostly for use in mining. It is made by combining <a href="https://www.britannica.com/science/ammonia">ammonia</a> gas with liquid nitric acid, which itself is made from ammonia.</p>
<p>Ammonium nitrate is classified as <a href="http://www.dmp.wa.gov.au/Dangerous-Goods/What-is-a-dangerous-good-4411.aspx">dangerous goods</a> and all aspects of its use are tightly regulated. For decades, Australia has produced, stored and used ammonium nitrate without a <a href="https://www.abc.net.au/news/2014-09-07/ammonium-nitrate-truck-explosion-site/5725904?nw=0"><em>major</em></a> incident. </p>
<p>The explosion in Beirut shows us just how important these regulations are.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/75-years-after-hiroshima-and-nagasaki-the-vatican-is-providing-moral-guidance-on-nuclear-weapons-140615">75 years after Hiroshima and Nagasaki, the Vatican is providing moral guidance on nuclear weapons</a>
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<img src="https://counter.theconversation.com/content/143979/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Gabriel da Silva does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>For combustion to occur, oxygen must be present. Ammonium nitrate prills provide a much more concentrated supply of oxygen than the air around us.Gabriel da Silva, Associate Professor of Chemical Engineering, The University of MelbourneLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1153672019-06-11T20:12:02Z2019-06-11T20:12:02ZSilver makes beautiful bling but it’s also good for keeping the bacterial bugs away<figure><img src="https://images.theconversation.com/files/278843/original/file-20190611-32321-k3juqs.jpg?ixlib=rb-1.1.0&rect=148%2C107%2C4940%2C3145&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Silver has been used to make jewellery for centuries but it's also good at killing bacteria and could be used in new antibiotics.</span> <span class="attribution"><span class="source">Shutterstock/Santi S</span></span></figcaption></figure><p><em>To mark the <a href="https://www.iypt2019.org/">International Year of the Periodic Table of Chemical Elements</a> we’re taking a look at some of the elements used by researchers in their work.</em></p>
<p><em>Today’s focus is silver, an element seen as a marker of second place – but this reputation is undeserved.</em></p>
<hr>
<p><a href="http://www.rsc.org/periodic-table/element/47/silver">Silver</a> has long played second fiddle to other elements. In sport, it is the symbol of second place, giving way to gold in the medals. In jewellery, airline frequent flyer programs and credit cards, silver is also topped by gold and platinum.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/278825/original/file-20190611-32342-jp4knh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/278825/original/file-20190611-32342-jp4knh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/278825/original/file-20190611-32342-jp4knh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/278825/original/file-20190611-32342-jp4knh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/278825/original/file-20190611-32342-jp4knh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/278825/original/file-20190611-32342-jp4knh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/278825/original/file-20190611-32342-jp4knh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Hold that silver high! Proud medal winners from the Sochi Winter Olympics, 2014.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/andymiah/12515487734/">Flickr/Andy Miah</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span>
</figcaption>
</figure>
<p>But in the world of useful elements, silver should be gold.</p>
<p>My interest in silver originated when growing up in Canada, searching through loose change for pre-1968 quarters (25 cents) that were made from 80% silver (currently worth at least <a href="https://www.ngccoin.com/price-guide/series-detail.aspx?MVDetailID=55&Series=Canada-Silver-Quarter">US$2.24 each</a>).</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/from-the-bronze-age-to-food-cans-heres-how-tin-changed-humanity-114195">From the bronze age to food cans, here's how tin changed humanity</a>
</strong>
</em>
</p>
<hr>
<p>More recently, in my <a href="http://www.aidrc.org.au/mark-blaskovich">current scientific role fighting antimicrobial resistance</a>, my interest has been piqued by silver’s association with killing bacteria.</p>
<h2>The silver medical treatment</h2>
<p>Silver has a <a href="https://www.sciencedirect.com/science/article/pii/S0734975018300946" title="Silver bullets: A new lustre on an old antimicrobial agent">long history of antibacterial activity</a>. The Phoenicians lined clay vessels with silver to preserve liquids (around 1300BCE), the Persians and Greeks used silver containers to store drinking water (around 5000-300BCE) and Americans travelling west during the 1880s added silver coins into water barrels. </p>
<p>More recently, <a href="https://www.sciencedirect.com/science/article/pii/S0305417914003040" title="Silver in medicine: A brief history BC 335 to present">both American and Russian space programs have used ionic silver to purify water</a>, including <a href="https://www.space.news/2016-06-06-nasa-open-to-using-silver-treated-water-in-space-despite-fda-opposition.html">on the International Space Station</a>. </p>
<p>Colloidal silver, a suspension of very small nanoparticles of silver metal, has found widespread use as a popular home remedy for a range of ailments, but is often marketed with <a href="https://www.quackwatch.org/01QuackeryRelatedTopics/PhonyAds/silverad.html">dubious claims</a> and is <a href="https://nccih.nih.gov/health/colloidalsilver">not supported by the scientific community</a>.</p>
<p>Some <a href="https://www.purestcolloids.com/history-silver.php">websites claim</a> the use of silver cutlery and dinnerware by wealthy Europeans in the Middle Ages may have helped favour their survival during the bubonic plague, though evidence supporting this is scant.</p>
<p>On a related note, one version of the <a href="https://www.quora.com/How-did-the-term-Blue-Blood-come-about">origin of the term “blue blood”</a> to describe the wealthy is based on their use of silver dinnerware, with significant silver ion ingestion known to cause <a href="https://www.merriam-webster.com/medical/argyria">argyria</a>, or purple-grey skin.</p>
<p>Despite these nonscientific associations, silver has found widespread acceptance in the medical community for specific applications of its antibacterial properties. </p>
<h2>Silver for burns</h2>
<p>Silver nitrate solutions were found to prevent eye infections in newborns in the 1880s, and were still commonly used for this in the 1970s. Solutions were also used to treat burn injuries, leading to many scientific reports in the 1960s, such as a <a href="https://nyaspubs.onlinelibrary.wiley.com/doi/abs/10.1111/j.1749-6632.1968.tb14745.x" title="THE TREATMENT OF EXTENSIVE THERMAL BURNS WITH 0.5% SILVER NITRATE SOLUTION">1968 study on treating extensive thermal burns with 0.5% silver nitrate solution</a> that describes an apparent reduction in death. </p>
<p>Both 0.5% silver nitrate solution and 1% silver sulfadiazine cream are still used in burn care and are accompanied by new silver-based wound dressings. </p>
<p>The antimicrobial use of silver has crept into consumer products, such as <a href="https://www.elastoplast.com.au/products/wound-care/antibacterial-fabric-plaster">antibacterial bandages</a>, <a href="http://thefootshop.com.au/products/carnation-footcare-silversock-black.html">socks</a> and <a href="https://www.nivea.com.au/products/nivea-men-silver-protect-roll-on-deodorant-40058083072720031.html">deodorants</a>, and antibacterial coatings on a range of products such as <a href="https://www.samsung.com/in/support/home-appliances/how-does-silver-nano-coating-help/">refrigerators</a>. </p>
<p>While this may sound like a good idea, there are concerns that widespread use of silver could cause <a href="https://www.nursingtimes.net/clinical-archive/infection-control/bacterial-resistance-to-silver-based-antibiotics/201749.article">bacteria to become resistant</a>, not only to silver, but also to our important antibiotics.</p>
<p>It’s not known exactly how silver kills bacteria, <a href="https://www.sciencedirect.com/science/article/pii/S1549963415006000" title="Silver nanoparticles: A new view on mechanistic aspects on antimicrobial activity">but it seems to work by multiple mechanisms</a>, including cell membrane damage and free radical generation. </p>
<p>Our work on silver is looking at whether it can help existing antibiotics work more effectively, especially against resistant bacteria. This research, which has been ongoing for more than five years, has identified that there is better synergy between silver and some types of antibiotics than others, but we don’t yet know why. </p>
<p>Eventually, this research could lead to new formulations of antibiotics with better activity, where the actual antibiotic remains the same but it is delivered as a salt with silver, instead of a more common ion like sodium.</p>
<h2>The silver resources</h2>
<p>The actual word silver stems from the Anglo-Saxon name for it, siolfur, while its chemical symbol Ag comes from the Latin name for silver, argentum.</p>
<p>Silver can sometimes be found as nuggets of pure metal, though this form is more rare than gold. Most often it is found combined with other elements in ores such as argentite (with sulfur) or galena (with lead).</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/278823/original/file-20190611-32335-1ggjcxg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/278823/original/file-20190611-32335-1ggjcxg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/278823/original/file-20190611-32335-1ggjcxg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/278823/original/file-20190611-32335-1ggjcxg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/278823/original/file-20190611-32335-1ggjcxg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/278823/original/file-20190611-32335-1ggjcxg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/278823/original/file-20190611-32335-1ggjcxg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/278823/original/file-20190611-32335-1ggjcxg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Not so shiny yet, a lump of silver ore.</span>
<span class="attribution"><span class="source">Shutterstock/hecke</span></span>
</figcaption>
</figure>
<p>The ores are mined and the silver generally removed by smelting (heating combined with chemical reactions). It is believed this technique was discovered before 2000BCE.</p>
<p>Historically, the major use of silver has been as coinage and in jewellery. Traditional photography uses silver halides for the photosensitive film, while mirror backings and Christmas ornaments use silver-plated glass.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/titanium-is-the-perfect-metal-to-make-replacement-human-body-parts-115361">Titanium is the perfect metal to make replacement human body parts</a>
</strong>
</em>
</p>
<hr>
<p>Silver lies in the middle of the <a href="https://www.raci.org.au/periodic-table-on-show">periodic table</a>. It is encircled by other useful and well-known metals such as (clockwise from above) copper, zinc, cadmium, mercury, gold, platinum, palladium and nickel. </p>
<p>I would argue that silver shines brightly above its neighbours – it actually does, as it has the highest reflectivity of any metal – and also is the best at conducting electricity and heat.</p>
<p>So silver really does deserves top of the podium: a gold for silver!</p>
<hr>
<p><em>If you’re an academic researcher working with a particular element from the periodic table and have an interesting story to tell then why not <a href="https://theconversation.com/au/pitches">get in touch</a>.</em></p><img src="https://counter.theconversation.com/content/115367/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mark Blaskovich has received funding from government and industry to investigate the antimicrobial activity of silver in combination with other compounds.</span></em></p>For too long silver has been used to mark second best but this element deserves more recognition thanks to its antibacterial properties.Mark Blaskovich, Senior Research Officer, The University of QueenslandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1068992019-01-02T09:12:42Z2019-01-02T09:12:42ZThe periodic table is 150 – but it could have looked very different<figure><img src="https://images.theconversation.com/files/249935/original/file-20181211-76968-1lsh5rp.png?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Theodor Benfey's spira table (1964).</span> <span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/Category:Alternative_forms_of_periodic_table#/media/File:Elementspiral_(polyatomic).svg">DePiep/Wikipedia</a></span></figcaption></figure><p>The <a href="https://theconversation.com/the-periodic-table-from-its-classic-design-to-use-in-popular-culture-52822">periodic table </a> stares down from the walls of just about every chemistry lab. The credit for its creation generally goes to <a href="http://www.rsc.org/education/teachers/resources/periodictable/pre16/develop/mendeleev.htm">Dimitri Mendeleev</a>, a Russian chemist who in 1869 wrote out the known elements (of which there were 63 at the time) on cards and then arranged them in columns and rows according to their chemical and physical properties. To celebrate the 150th anniversary of this pivotal moment in science, the UN has proclaimed 2019 to be the <a href="https://iupac.org/united-nations-proclaims-international-year-periodic-table-chemical-elements/">International year of the Periodic Table</a>.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/249435/original/file-20181207-128205-1xfg95r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/249435/original/file-20181207-128205-1xfg95r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/249435/original/file-20181207-128205-1xfg95r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=786&fit=crop&dpr=1 600w, https://images.theconversation.com/files/249435/original/file-20181207-128205-1xfg95r.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=786&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/249435/original/file-20181207-128205-1xfg95r.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=786&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/249435/original/file-20181207-128205-1xfg95r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=988&fit=crop&dpr=1 754w, https://images.theconversation.com/files/249435/original/file-20181207-128205-1xfg95r.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=988&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/249435/original/file-20181207-128205-1xfg95r.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=988&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">John Dalton’s element list.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Dalton%27s_Element_List.jpg">Wikimedia Commons</a></span>
</figcaption>
</figure>
<p>But the periodic table didn’t actually start with Mendeleev. Many had tinkered with arranging the elements. Decades before, chemist John Dalton tried to <a href="http://www.sussexvt.k12.de.us/science/the%20history%20of%20the%20world%201500-1899/john%20dalton%27s%20periodic%20tables.htm">create a table</a> as well as some rather interesting symbols for the elements (they didn’t catch on). And just a few years before Mendeleev sat down with his deck of homemade cards, <a href="https://www.britannica.com/biography/John-Newlands">John Newlands</a> also created a table sorting the elements by their properties.</p>
<p>Mendeleev’s genius was in what he left out of his table. He recognised that certain elements were missing, yet to be discovered. So where Dalton, Newlands and others had laid out what was known, Mendeleev left space for the unknown. Even more amazingly, he accurately predicted the properties of the missing elements.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/249713/original/file-20181210-76959-1jny1g2.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/249713/original/file-20181210-76959-1jny1g2.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/249713/original/file-20181210-76959-1jny1g2.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=350&fit=crop&dpr=1 600w, https://images.theconversation.com/files/249713/original/file-20181210-76959-1jny1g2.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=350&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/249713/original/file-20181210-76959-1jny1g2.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=350&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/249713/original/file-20181210-76959-1jny1g2.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=440&fit=crop&dpr=1 754w, https://images.theconversation.com/files/249713/original/file-20181210-76959-1jny1g2.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=440&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/249713/original/file-20181210-76959-1jny1g2.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=440&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Dimitry Mendeleev’s table complete with missing elements.</span>
<span class="attribution"><span class="source">Wikimedia Commons</span></span>
</figcaption>
</figure>
<p>Notice the question marks in his table above? For example, next to Al (aluminium) there’s space for an unknown metal. Mendeleev foretold it would have an atomic mass of 68, a density of six grams per cubic centimetre and a very low melting point. Six years later <a href="https://www.lindahall.org/paul-emile-lecoq-de-boisbaudran/">Paul Émile Lecoq de Boisbaudran,</a> isolated <a href="http://www.rsc.org/periodic-table/element/31/gallium">gallium</a> and sure enough it slotted right into the gap with an atomic mass of 69.7, a density of 5.9g/cm³ and a melting point so low that <a href="https://www.youtube.com/watch?v=N6ccRvKKwZQ">it becomes liquid in your hand</a>. Mendeleev did the same for <a href="https://www.meta-synthesis.com/webbook/35_pt/pt_database.php?PT_id=303">scandium, germanium</a> and <a href="http://www.rsc.org/periodic-table/element/43/technetium">technetium</a> (which wasn’t discovered until 1937, 30 years after his death).</p>
<p>At first glance Mendeleev’s table doesn’t look much like the one we are familiar with. For one thing, the modern table has a bunch of elements that Mendeleev overlooked (and failed to leave room for), most notably the noble gases (such as helium, neon, argon). And the table is oriented differently to our modern version, with elements we now place together in columns arranged in rows.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/249442/original/file-20181207-128193-vpgzxa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/249442/original/file-20181207-128193-vpgzxa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/249442/original/file-20181207-128193-vpgzxa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=318&fit=crop&dpr=1 600w, https://images.theconversation.com/files/249442/original/file-20181207-128193-vpgzxa.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=318&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/249442/original/file-20181207-128193-vpgzxa.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=318&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/249442/original/file-20181207-128193-vpgzxa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=400&fit=crop&dpr=1 754w, https://images.theconversation.com/files/249442/original/file-20181207-128193-vpgzxa.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=400&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/249442/original/file-20181207-128193-vpgzxa.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=400&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Today’s periodic table.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/File:Simple_Periodic_Table_Chart-en.svg">Offnfopt/Wikipedia</a></span>
</figcaption>
</figure>
<p>But once you give Mendeleev’s table a 90-degree turn, the similarity to the modern version becomes apparent. For example, the halogens – fluorine (F), chlorine (Cl), bromine (Br), and Iodine (I) (the J symbol in Mendeleev’s table) – all appear next to one another. Today they are arranged in the table’s 17th column (or group 17 as chemists prefer to call it).</p>
<h2>Period of experimentation</h2>
<p>It may seem a small leap from this to the familiar diagram but, years after Mendeleev’s publications, there was plenty of experimentation with alternative layouts for the elements. Even before the table got its permanent right-angle flip, folks suggested some weird and wonderful twists.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/249444/original/file-20181207-128187-1dgwvl6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/249444/original/file-20181207-128187-1dgwvl6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/249444/original/file-20181207-128187-1dgwvl6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=630&fit=crop&dpr=1 600w, https://images.theconversation.com/files/249444/original/file-20181207-128187-1dgwvl6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=630&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/249444/original/file-20181207-128187-1dgwvl6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=630&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/249444/original/file-20181207-128187-1dgwvl6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=791&fit=crop&dpr=1 754w, https://images.theconversation.com/files/249444/original/file-20181207-128187-1dgwvl6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=791&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/249444/original/file-20181207-128187-1dgwvl6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=791&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Heinrich Baumhauer’s spiral.</span>
<span class="attribution"><span class="source">Reprinted (adapted) with permission from Types of graphic classifications of the elements. III. Spiral, helical, and miscellaneous charts, G. N. Quam, Mary Battell Quam. Copyright (1934) American Chemical Society.</span></span>
</figcaption>
</figure>
<p>One particularly striking example is Heinrich <a href="https://www.meta-synthesis.com/webbook/35_pt/JCE_PTs_1934.pdf">Baumhauer’s spiral</a>, published in 1870, with hydrogen at its centre and elements with increasing atomic mass spiralling outwards. The elements that fall on each of the wheel’s spokes share common properties just as those in a column (group) do so in today’s table. There was also Henry Basset’s <a href="http://www.chem.msu.ru/eng/misc/mendeleev/hyper/">rather odd “dumb-bell”</a> formulation of 1892.</p>
<p>Nevertheless, by the beginning of the 20th century, the table had settled down into a familiar horizontal format with the <a href="https://www.meta-synthesis.com/webbook/35_pt/JCE_PTs_1934_medium.pdf">strikingly modern looking version from Alfred Werner</a> in 1905. For the first time, the noble gases appeared in their now familiar position on the far right of the table. Werner also tried to take a leaf out of Mendeleev’s book by leaving gaps, although he rather overdid the guess work with suggestions for elements lighter than hydrogen and another sitting between hydrogen and helium (none of which exist).</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/249445/original/file-20181207-128196-1g58xp9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/249445/original/file-20181207-128196-1g58xp9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/249445/original/file-20181207-128196-1g58xp9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=227&fit=crop&dpr=1 600w, https://images.theconversation.com/files/249445/original/file-20181207-128196-1g58xp9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=227&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/249445/original/file-20181207-128196-1g58xp9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=227&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/249445/original/file-20181207-128196-1g58xp9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=285&fit=crop&dpr=1 754w, https://images.theconversation.com/files/249445/original/file-20181207-128196-1g58xp9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=285&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/249445/original/file-20181207-128196-1g58xp9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=285&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Alfred Werner’s modern incarnation.</span>
<span class="attribution"><span class="source">Reprinted (adapted) with permission from Types of graphic classifications of the elements. I. Introduction and short tables, G. N. Quam, Mary Battell Quam. Copyright (1934) American Chemical Society.</span></span>
</figcaption>
</figure>
<p>Despite this rather modern looking table, there was still a bit of rearranging to be done. Particularly influential was <a href="https://link.springer.com/article/10.1007/s10698-008-9062-5">Charles Janet’s</a> version. He took a physicist’s approach to the table and used a newly discovered <a href="https://theconversation.com/explainer-quantum-physics-570">quantum theory</a> to create a layout based on electron configurations. The resulting “<a href="https://www.sciencenews.org/blog/context/old-periodic-table-could-resolve-today%25E2%2580%2599s-element-placement-dispute">left step</a>” table is still preferred by many physicists. Interestingly, Janet also provided space for elements right up to number 120 despite only 92 being known at the time (we’re only at 118 now).</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/249448/original/file-20181207-128187-11i867s.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/249448/original/file-20181207-128187-11i867s.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/249448/original/file-20181207-128187-11i867s.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=140&fit=crop&dpr=1 600w, https://images.theconversation.com/files/249448/original/file-20181207-128187-11i867s.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=140&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/249448/original/file-20181207-128187-11i867s.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=140&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/249448/original/file-20181207-128187-11i867s.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=176&fit=crop&dpr=1 754w, https://images.theconversation.com/files/249448/original/file-20181207-128187-11i867s.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=176&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/249448/original/file-20181207-128187-11i867s.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=176&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Charles Janet’s left-step table.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Charles_Janet">Wikipedia</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>Settling on a design</h2>
<p>The modern table is actually <a href="https://www.meta-synthesis.com/webbook/documents/LEACH_Basic_Elemental_Property.pdf">a direct evolution of Janet’s version</a>. The alkali metals (the group topped by lithium) and the alkaline earth metals (topped by beryllium) got shifted from far right to the far left to create a very wide looking (long form) periodic table. The problem with this format is that it doesn’t fit nicely on a page or poster, so largely for aesthetic reasons the f-block elements are usually cut out and deposited below the main table. That’s how we arrived at the table we recognise today.</p>
<p>That’s not to say folks haven’t tinkered with layouts, often as an attempt to highlight correlations between elements that aren’t readily apparent in the conventional table. There are literally hundreds of variations (check out Mark Leach’s <a href="https://www.meta-synthesis.com/webbook/35_pt/pt_database.php">database</a>) with <a href="https://www.meta-synthesis.com/webbook/35_pt/pt_database.php?Button=Spiral+Formulations">spirals</a> and <a href="https://www.meta-synthesis.com/webbook/35_pt/pt_database.php?Button=3D+Formulations">3D versions</a> being particularly popular, not to mention more tongue-in-cheek variants.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/249485/original/file-20181207-128196-ie5nlv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/249485/original/file-20181207-128196-ie5nlv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=476&fit=crop&dpr=1 600w, https://images.theconversation.com/files/249485/original/file-20181207-128196-ie5nlv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=476&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/249485/original/file-20181207-128196-ie5nlv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=476&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/249485/original/file-20181207-128196-ie5nlv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=598&fit=crop&dpr=1 754w, https://images.theconversation.com/files/249485/original/file-20181207-128196-ie5nlv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=598&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/249485/original/file-20181207-128196-ie5nlv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=598&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">3D ‘Mendeleev flower’ version of the table.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/Category:Alternative_forms_of_periodic_table">Тимохова Ольга/Wikipedia</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>How about my <a href="https://universityofhull.app.box.com/v/elementstubemap">own fusion of two iconic graphics</a>, Mendeleev’s table and Henry Beck’s London Underground map below? </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/249481/original/file-20181207-128187-1stsxv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/249481/original/file-20181207-128187-1stsxv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/249481/original/file-20181207-128187-1stsxv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=424&fit=crop&dpr=1 600w, https://images.theconversation.com/files/249481/original/file-20181207-128187-1stsxv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=424&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/249481/original/file-20181207-128187-1stsxv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=424&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/249481/original/file-20181207-128187-1stsxv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=533&fit=crop&dpr=1 754w, https://images.theconversation.com/files/249481/original/file-20181207-128187-1stsxv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=533&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/249481/original/file-20181207-128187-1stsxv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=533&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The author’s underground map of the elements.</span>
<span class="attribution"><span class="source">Mark Lorch</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Or the dizzy array of imitations that aim to give a science feel to categorising everything from <a href="http://ecx.images-amazon.com/images/I/81CFIrGYpzL._SL1500_.jpg">beer</a> to <a href="https://ohmy.disney.com/wp-content/uploads/sites/25/2015/03/omd_periodictableofdisney_final.jpg">Disney characters</a>, and my particular favourite “<a href="http://www.crispian.net/PTIR/Nonsense.html">irrational nonsense</a>”. All of which go to show how the periodic table of elements has become the iconic symbol of science.</p><img src="https://counter.theconversation.com/content/106899/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mark Lorch does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>There have been some rather wacky looking suggestions for arranging the chemical elements.Mark Lorch, Professor of Science Communication and Chemistry, University of HullLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/947002018-05-23T10:39:19Z2018-05-23T10:39:19ZThe Standard Model of particle physics: The absolutely amazing theory of almost everything<figure><img src="https://images.theconversation.com/files/219824/original/file-20180521-14978-36nv6i.jpg?ixlib=rb-1.1.0&rect=174%2C0%2C977%2C649&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">How does our world work on a subatomic level?</span> <span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Varsha_ys.jpg">Varsha Y S</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>The Standard Model. What a dull name for the most accurate scientific theory known to human beings.</p>
<p>More than a quarter of the Nobel Prizes in physics of the last century are direct inputs to or direct results of the Standard Model. Yet its name suggests that if you can afford a few extra dollars a month you should buy the upgrade. <a href="https://scholar.google.com/citations?user=eQiX0m4AAAAJ&hl=en&oi=ao">As a theoretical physicist</a>, I’d prefer The Absolutely Amazing Theory of Almost Everything. That’s what the Standard Model really is.</p>
<p>Many recall the excitement among scientists and media over the 2012 <a href="https://home.cern/topics/higgs-boson">discovery of the Higgs boson</a>. But that much-ballyhooed event didn’t come out of the blue – it capped a five-decade undefeated streak for the Standard Model. Every fundamental force but gravity is included in it. Every attempt to overturn it to demonstrate in the laboratory that it must be substantially reworked – and there have been many over the past 50 years – has failed. </p>
<p>In short, the <a href="https://home.cern/about/physics/standard-model">Standard Model</a> answers this question: What is everything made of, and how does it hold together?</p>
<h2>The smallest building blocks</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/219828/original/file-20180521-14991-vlfgkx.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/219828/original/file-20180521-14991-vlfgkx.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/219828/original/file-20180521-14991-vlfgkx.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=424&fit=crop&dpr=1 600w, https://images.theconversation.com/files/219828/original/file-20180521-14991-vlfgkx.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=424&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/219828/original/file-20180521-14991-vlfgkx.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=424&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/219828/original/file-20180521-14991-vlfgkx.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=533&fit=crop&dpr=1 754w, https://images.theconversation.com/files/219828/original/file-20180521-14991-vlfgkx.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=533&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/219828/original/file-20180521-14991-vlfgkx.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=533&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">But these elements can be broken down further.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Periodic_table_vectorial.png">Rubén Vera Koster</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>You know, of course, that the world around us is made of molecules, and molecules are made of atoms. Chemist <a href="https://www.famousscientists.org/dmitri-mendeleev/">Dmitri Mendeleev</a> figured out in the 1860s how to organize all atoms – that is, the elements – into the periodic table that you probably studied in middle school. But there are 118 different chemical elements. There’s antimony, arsenic, aluminum, selenium … and 114 more.</p>
<p>Physicists like things simple. We want to boil things down to their essence, a few basic building blocks. Over a hundred chemical elements is not simple. The ancients believed that everything is made of just five elements – <a href="https://en.wikipedia.org/wiki/Classical_element">earth, water, fire, air and aether</a>. Five is much simpler than 118. It’s also wrong. </p>
<p>By 1932, scientists knew that all those atoms are made of just three particles – neutrons, protons and electrons. The neutrons and protons are bound together tightly into the nucleus. The electrons, thousands of times lighter, whirl around the nucleus at speeds approaching that of light. Physicists <a href="https://www.nobelprize.org/nobel_prizes/physics/laureates/1918/planck-bio.html">Planck</a>, <a href="https://www.nobelprize.org/nobel_prizes/physics/laureates/1922/bohr-bio.html">Bohr</a>, <a href="https://www.nobelprize.org/nobel_prizes/physics/laureates/1933/schrodinger-bio.html">Schroedinger</a>, <a href="https://www.nobelprize.org/nobel_prizes/physics/laureates/1932/heisenberg-bio.html">Heisenberg</a> and friends had invented a new science – <a href="https://en.wikipedia.org/wiki/Quantum_mechanics">quantum mechanics</a> – to explain this motion.</p>
<p>That would have been a satisfying place to stop. Just three particles. Three is even simpler than five. But held together how? The negatively charged electrons and positively charged protons are bound together by <a href="https://en.wikipedia.org/wiki/Electromagnetism">electromagnetism</a>. But the protons are all huddled together in the nucleus and their positive charges should be pushing them powerfully apart. The neutral neutrons can’t help. </p>
<p>What binds these protons and neutrons together? “Divine intervention” a man on a Toronto street corner told me; he had a pamphlet, I could read all about it. But this scenario seemed like a lot of trouble even for a divine being – keeping tabs on every single one of the universe’s 10⁸⁰ protons and neutrons and bending them to its will. </p>
<h2>Expanding the zoo of particles</h2>
<p>Meanwhile, nature cruelly declined to keep its zoo of particles to just three. Really four, because we should count the <a href="https://en.wikipedia.org/wiki/Photon">photon</a>, the particle of light that <a href="https://www.nobelprize.org/nobel_prizes/physics/laureates/1921/einstein-bio.html">Einstein</a> described. Four grew to five when <a href="https://www.nobelprize.org/nobel_prizes/physics/laureates/1936/anderson-bio.html">Anderson</a> measured electrons with positive charge – positrons – striking the Earth from outer space. At least <a href="https://www.nobelprize.org/nobel_prizes/physics/laureates/1933/dirac-bio.html">Dirac</a> had predicted these first anti-matter particles. Five became six when the pion, which <a href="https://www.nobelprize.org/nobel_prizes/physics/laureates/1949/yukawa-bio.html">Yukawa</a> predicted would hold the nucleus together, was found. </p>
<p>Then came the muon – 200 times heavier than the electron, but otherwise a twin. “Who ordered that?” <a href="https://www.nobelprize.org/nobel_prizes/physics/laureates/1944/rabi-bio.html">I.I. Rabi</a> quipped. That sums it up. Number seven. Not only not simple, redundant.</p>
<p>By the 1960s there were hundreds of “fundamental” particles. In place of the well-organized periodic table, there were just long lists of baryons (heavy particles like protons and neutrons), mesons (like <a href="https://en.wikipedia.org/wiki/Hideki_Yukawa">Yukawa</a>’s pions) and leptons (light particles like the electron, and the elusive neutrinos) – with no organization and no guiding principles.</p>
<p>Into this breach sidled the Standard Model. It was not an overnight flash of brilliance. No Archimedes leapt out of a bathtub shouting “eureka.” Instead, there was a series of crucial insights by a few key individuals in the mid-1960s that transformed this quagmire into a simple theory, and then five decades of experimental verification and theoretical elaboration. </p>
<p><a href="https://home.cern/about/updates/2014/01/fifty-years-quarks">Quarks</a>. They come in six varieties we call flavors. Like ice cream, except not as tasty. Instead of vanilla, chocolate and so on, we have up, down, strange, charm, bottom and top. In 1964, <a href="https://www.nobelprize.org/nobel_prizes/physics/laureates/1969/gell-mann-bio.html">Gell-Mann</a> and <a href="https://www.macfound.org/fellows/113/">Zweig</a> taught us the recipes: Mix and match any three quarks to get a baryon. Protons are two ups and a down quark bound together; neutrons are two downs and an up. Choose one quark and one antiquark to get a meson. A pion is an up or a down quark bound to an anti-up or an anti-down. All the material of our daily lives is made of just up and down quarks and anti-quarks and electrons.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/219958/original/file-20180522-51127-4tx5tr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/219958/original/file-20180522-51127-4tx5tr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/219958/original/file-20180522-51127-4tx5tr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=536&fit=crop&dpr=1 600w, https://images.theconversation.com/files/219958/original/file-20180522-51127-4tx5tr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=536&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/219958/original/file-20180522-51127-4tx5tr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=536&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/219958/original/file-20180522-51127-4tx5tr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=673&fit=crop&dpr=1 754w, https://images.theconversation.com/files/219958/original/file-20180522-51127-4tx5tr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=673&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/219958/original/file-20180522-51127-4tx5tr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=673&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The Standard Model of elementary particles provides an ingredients list for everything around us.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Standard_Model_From_Fermi_Lab.jpg">Fermi National Accelerator Laboratory</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Simple. Well, simple-ish, because keeping those quarks bound is a feat. They are tied to one another so tightly that you never ever find a quark or anti-quark on its own. The theory of that binding, and the particles called gluons (chuckle) that are responsible, is called <a href="https://en.wikipedia.org/wiki/Quantum_chromodynamics">quantum chromodynamics</a>. It’s a vital piece of the Standard Model, but mathematically difficult, even posing an unsolved problem of basic mathematics. We physicists do our best to calculate with it, but we’re still learning how.</p>
<p>The other aspect of the Standard Model is “<a href="https://doi.org/10.1103/PhysRevLett.19.1264">A Model of Leptons</a>.” That’s the name of the landmark 1967 paper by <a href="https://www.nobelprize.org/nobel_prizes/physics/laureates/1979/weinberg-bio.html">Steven Weinberg</a> that pulled together quantum mechanics with the vital pieces of knowledge of how particles interact and organized the two into a single theory. It incorporated the familiar electromagnetism, joined it with what physicists called “the weak force” that causes certain radioactive decays, and explained that they were different aspects of the same force. It incorporated <a href="https://www.nobelprize.org/nobel_prizes/physics/laureates/2013/higgs-facts.html">the Higgs mechanism</a> for giving mass to fundamental particles. </p>
<p>Since then, the Standard Model has predicted the results of experiment after experiment, including the discovery of several varieties of quarks and of the <a href="https://en.wikipedia.org/wiki/W_and_Z_bosons">W and Z bosons</a> – heavy particles that are for weak interactions what the photon is for electromagnetism. The possibility that <a href="https://en.wikipedia.org/wiki/Neutrino#Mass">neutrinos aren’t massless</a> was overlooked in the 1960s, but slipped easily into the Standard Model in the 1990s, a few decades late to the party.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/219960/original/file-20180522-51095-vverdp.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/219960/original/file-20180522-51095-vverdp.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/219960/original/file-20180522-51095-vverdp.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=385&fit=crop&dpr=1 600w, https://images.theconversation.com/files/219960/original/file-20180522-51095-vverdp.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=385&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/219960/original/file-20180522-51095-vverdp.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=385&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/219960/original/file-20180522-51095-vverdp.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=484&fit=crop&dpr=1 754w, https://images.theconversation.com/files/219960/original/file-20180522-51095-vverdp.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=484&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/219960/original/file-20180522-51095-vverdp.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=484&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">3D view of an event recorded at the CERN particle accelerator showing characteristics expected from the decay of the SM Higgs boson to a pair of photons (dashed yellow lines and green towers).</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:3D_view_of_an_event_recorded_with_the_CMS_detector_in_2012_at_a_proton-proton_centre_of_mass_energy_of_8_TeV.png">McCauley, Thomas; Taylor, Lucas; for the CMS Collaboration CERN</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Discovering the Higgs boson in 2012, long predicted by the Standard Model and long sought after, was a thrill but not a surprise. It was yet another crucial victory for the Standard Model over the dark forces that particle physicists have repeatedly warned loomed over the horizon. Concerned that the Standard Model didn’t adequately embody their expectations of simplicity, worried about its mathematical self-consistency, or looking ahead to the eventual necessity to bring the force of gravity into the fold, physicists have made numerous proposals for theories beyond the Standard Model. These bear exciting names like <a href="https://en.wikipedia.org/wiki/Grand_Unified_Theory">Grand Unified Theories</a>, <a href="https://en.wikipedia.org/wiki/Supersymmetry">Supersymmetry</a>, <a href="https://en.wikipedia.org/wiki/Technicolor_(physics)">Technicolor</a>, and <a href="https://en.wikipedia.org/wiki/String_theory">String Theory</a>. </p>
<p>Sadly, at least for their proponents, beyond-the-Standard-Model theories have not yet successfully predicted any new experimental phenomenon or any experimental discrepancy with the Standard Model.</p>
<p>After five decades, far from requiring an upgrade, the Standard Model is <a href="http://artsci.case.edu/smat50/">worthy of celebration</a> as the Absolutely Amazing Theory of Almost Everything.</p><img src="https://counter.theconversation.com/content/94700/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Glenn Starkman receives funding from the Office of Science of the US Department of Energy. He is affiliated with Case Western Reserve University. </span></em></p>A particle physicist explains just what this keystone theory includes. After 50 years, it’s the best we’ve got to answer what everything in the universe is made of and how it all holds together.Glenn Starkman, Distinguished University Professor of Physics, Case Western Reserve UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/903912018-01-23T19:12:29Z2018-01-23T19:12:29ZCurious Kids: How do scientists work out how old the Earth is?<figure><img src="https://images.theconversation.com/files/202744/original/file-20180122-110097-12vj03h.png?ixlib=rb-1.1.0&rect=0%2C0%2C2995%2C1320&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">It turns out that the world is about 4,600,000,000 years old. That's 4.6 billion years. That's pretty old!</span> <span class="attribution"><span class="source">Marcella Cheng/The Conversation</span>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span></figcaption></figure><p><em>This is an article from <a href="https://theconversation.com/au/topics/curious-kids-36782">Curious Kids</a>, a series for children. The Conversation is asking kids to send in questions they’d like an expert to answer. All questions are welcome – serious, weird or wacky!</em> </p>
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<blockquote>
<p><strong>How do scientists work out how old the Earth is? Leo, age 5, Geelong West.</strong></p>
</blockquote>
<p>Well, Leo, the world is actually like a big clock. We just need to know how to read the clock. To do that, we have to think about what the world is made of. </p>
<p>The world, and everything in it, is actually made of something very small called “elements”. These are the tiny, tiny building blocks of everything. You might have heard the names of some elements before. Gold is an element, and so is silver. There are lots of other elements too, with strange names like krypton and selenium and plutonium. There are about 118 different elements on Earth that we know about so far.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/explainer-what-is-radiocarbon-dating-and-how-does-it-work-9690">Explainer: what is radiocarbon dating and how does it work?</a>
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</em>
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<p>Most of these elements don’t change and stay the way they are forever. Scientists call these ones “stable” elements. </p>
<p>But there is a second sort of element that actually changes into something else over time. These aren’t as common, but they are in everything. They’re called “unstable” or “radioactive” elements.</p>
<p>Imagine that - some part of you is actually changing into something else! But don’t worry, most of these change over a very, very long time. Some take billions of years to do any really serious changing. </p>
<p>Your teeth have an element called potassium that is one of these changing elements. Your TV, computer, the soil in your garden – everything, really – has some of these changing elements. The changing process is called “radioactive decay”.</p>
<p>As you might have guessed, rocks also have these unstable elements in them. And we’ve measured out how long it takes for one of these elements to change into another one. </p>
<p>For example, if we had some stuff that contained an unstable element called <sup>14</sup>C (to say out loud, this is “carbon 14”), we know it takes about 5,730 years for about half of all the <sup>14</sup>C in our sample to change into another element called <sup>14</sup>N (pronounced as “nitrogen 14”).</p>
<p>Knowing how fast these elements change from one thing into another thing gives us a very big clue about how old the Earth is. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/202758/original/file-20180122-110100-1uen2yg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/202758/original/file-20180122-110100-1uen2yg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/202758/original/file-20180122-110100-1uen2yg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/202758/original/file-20180122-110100-1uen2yg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/202758/original/file-20180122-110100-1uen2yg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/202758/original/file-20180122-110100-1uen2yg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/202758/original/file-20180122-110100-1uen2yg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/202758/original/file-20180122-110100-1uen2yg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Scientists using the same techniques to work out how old fossils are.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/skippy/452231025/in/photolist-FXNwD-brVUa-9TYo4-foH1Sj-7yC3NV-LyGgG-oH9Hbw-7qGxb1-7BTRZe-3VwGHj-6rcG8U-qEwTLj-aH4QYR-6rcMy9-nGUwUy-k6rwa1-xBLms1-VsqnT7-adHvfz-bs4aEL-UkFeMr-7gXqBj-pmVKXa-22s4SY3-TzTWU5-WetkBY-yYbuwy-7gXokN-prE9br-bi7KjT-5qFrF3-9Dggzr-TUNEQ3-5cgiEa-7shDR8-VApJyE-aJcsdV-VstT2X-9keehg-aELxKE-7aU1eK-djmV9Z-4xkaao-VstTMe-2p8Yhx-4xkaty-a8zjJ7-jdzSh5-4n1mdj-4oyRma">Flickr/Scott</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-do-bees-ever-accidentally-sting-other-bees-82818">Curious Kids: Do bees ever accidentally sting other bees?</a>
</strong>
</em>
</p>
<hr>
<p>So how do we measure how old the Earth is? </p>
<p>Well, first we measure how much of the unstable elements are still left in the rocks of the Earth - these are the elements that haven’t changed yet, but <em>will</em> change over time because we know they’re unstable. </p>
<p>Then we measure the amount of the element they change <em>into</em>. </p>
<p>Once we know this, and we know how long the change takes, we can work out how old the world is! </p>
<p>It turns out that the world is about 4,600,000,000 years old. That’s 4.6 billion years. That’s pretty old!</p>
<hr>
<p><em>Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question to us. You can:</em></p>
<p><em>* Email your question to curiouskids@theconversation.edu.au
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* Tell us on <a href="https://twitter.com/ConversationEDU">Twitter</a> by tagging <a href="https://twitter.com/ConversationEDU">@ConversationEDU</a> with the hashtag #curiouskids, or
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<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=376&fit=crop&dpr=1 600w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=376&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=376&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=472&fit=crop&dpr=1 754w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=472&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=472&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
<span class="attribution"><a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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</figure>
<p><em>Please tell us your name, age and which city you live in. You can send an audio recording of your question too, if you want. Send as many questions as you like! We won’t be able to answer every question but we will do our best.</em></p><img src="https://counter.theconversation.com/content/90391/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Alan Collins receives funding from the Australian Research Council</span></em></p>The world is made of tiny building blocks called ‘elements’. Scientists have worked out how fast some elements change into other elements. That gives us a very big clue about how old the Earth is.Alan Collins, Professor of Geology, University of AdelaideLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/528222017-04-02T19:32:41Z2017-04-02T19:32:41ZThe periodic table: from its classic design to use in popular culture<figure><img src="https://images.theconversation.com/files/113029/original/image-20160226-26723-15gnsbs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The periodic table of the elements on a T-shirt.</span> <span class="attribution"><a class="source" href="http://mirror-au-nsw1.gallery.hd.org/_c/textures/_more2005/_more05/periodic-table-of-the-elements-printed-on-ancient-cotton-T-shirt-rotated-lowres-DHD.jpg.html">Damon Hart Davis</a></span></figcaption></figure><p>The periodic table is one of those classic images that you find in many science labs and classrooms. It’s an image almost everyone has seen at some time in their life.</p>
<p>You can also find the periodic table on <a href="https://www.questacon.edu.au/qshop/Questacon-Periodic-Table-T-shirt/">t-shirts</a>, <a href="http://shop.australiangeographic.com.au/mug-periodic-table.html">mugs</a>, <a href="https://www.getdigital.eu/Periodic-Table-Beach-Towel.html">beach towels</a>, <a href="https://www.amazon.com/Periodic-Chemical-Elements-Novelty-Pillowcase/dp/B00QFJXNVS">pillowcases</a> and <a href="http://www.cafepress.com.au/+periodic-table-chemical-elements+duvet-covers">duvet covers</a>, and <a href="http://www.cafepress.com.au/+periodic-table+gifts">plenty of other items</a>. It even inspired a <a href="https://www.theguardian.com/science/2009/oct/09/primo-levi-periodic-table">collection of short stories</a>. </p>
<p>Who can forget the periodic table put to music by the American <a href="http://www.allmusic.com/artist/tom-lehrer-mn0000611877/biography">Tom Lehrer</a>, a Harvard mathematics professor who was also a singer/songwriter and satirist. His song, The Elements, includes all the elements that were known at the time of writing in 1959.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/zGM-wSKFBpo?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>Since then, several new elements have been added to the periodic table, including the <a href="https://theconversation.com/four-new-elements-named-heres-how-the-periodic-table-evolved-60276">four</a> that were <a href="https://iupac.org/iupac-announces-the-names-of-the-elements-113-115-117-and-118/">formally approved last year</a> by the International Union of Pure and Applied Chemistry (IUPAC).</p>
<p>But what exactly does the periodic table show?</p>
<p>In brief, it is an attempt to organise the collection of the elements – all of the known pure compounds made from a single type of atom.</p>
<p>There are two ways to look at how the periodic table is constructed, based on either the observed properties of the elements contained within it, or on the subatomic construction of the atoms that form each element.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/155128/original/image-20170201-12656-1hd5emj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/155128/original/image-20170201-12656-1hd5emj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/155128/original/image-20170201-12656-1hd5emj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=385&fit=crop&dpr=1 600w, https://images.theconversation.com/files/155128/original/image-20170201-12656-1hd5emj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=385&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/155128/original/image-20170201-12656-1hd5emj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=385&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/155128/original/image-20170201-12656-1hd5emj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=484&fit=crop&dpr=1 754w, https://images.theconversation.com/files/155128/original/image-20170201-12656-1hd5emj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=484&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/155128/original/image-20170201-12656-1hd5emj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=484&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The basic modern periodic table.</span>
<span class="attribution"><span class="source">Shutterstock/duntaro</span></span>
</figcaption>
</figure>
<h2>The elements</h2>
<p>When scientists began collecting elements in the 1700s and 1800s, slowly identifying new ones over decades of research, they began to notice patterns and similarities in their physical properties. Some were gases, some were shiny metals, some reacted violently with water, and so on. </p>
<p>At the time when elements were first being discovered, the structure of atoms was not known. Scientists began to look at ways to arrange them systematically so that similar properties could be grouped together, just as someone collecting seashells might try to organise them by shape or colour.</p>
<p>The task was made more difficult because not all of the elements were known. This left gaps, which made deciphering patterns a bit like trying to assemble a jigsaw puzzle with missing pieces.</p>
<p>Different scientists came up with different types of tables. The first version of the current table is generally attributed to Russian chemistry professor <a href="http://www.britannica.com/biography/Dmitry-Ivanovich-Mendeleyev">Dmitri Mendeleev</a> in 1869, with an updated version in 1871.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/116741/original/image-20160330-28455-1ror2vj.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/116741/original/image-20160330-28455-1ror2vj.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/116741/original/image-20160330-28455-1ror2vj.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=350&fit=crop&dpr=1 600w, https://images.theconversation.com/files/116741/original/image-20160330-28455-1ror2vj.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=350&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/116741/original/image-20160330-28455-1ror2vj.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=350&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/116741/original/image-20160330-28455-1ror2vj.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=439&fit=crop&dpr=1 754w, https://images.theconversation.com/files/116741/original/image-20160330-28455-1ror2vj.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=439&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/116741/original/image-20160330-28455-1ror2vj.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=439&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Mendeleev’s periodic table is first published outside Russia in Zeitschrift für Chemie (1869, pages 405-6).</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Mendeleev%27s_periodic_table_(1869).svg">Wikimedia/Dimitri Mendeleev</a></span>
</figcaption>
</figure>
<p>Importantly, Mendeleev left gaps in the table where he thought missing elements should be placed. Over time, these gaps were filled in and the final version as we know it today emerged.</p>
<h2>The atoms</h2>
<p>To really understand the final structure of the periodic table, we need to understand a bit about atoms and how they are constructed. Atoms have a central core (the nucleus) made up of smaller particles called protons and neutrons.</p>
<p>It is the number of protons that gives an element its atomic number – the number generally found in the top left corner of each box in the periodic table. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/155129/original/image-20170201-12685-525wu2.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/155129/original/image-20170201-12685-525wu2.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/155129/original/image-20170201-12685-525wu2.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=195&fit=crop&dpr=1 600w, https://images.theconversation.com/files/155129/original/image-20170201-12685-525wu2.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=195&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/155129/original/image-20170201-12685-525wu2.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=195&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/155129/original/image-20170201-12685-525wu2.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=245&fit=crop&dpr=1 754w, https://images.theconversation.com/files/155129/original/image-20170201-12685-525wu2.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=245&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/155129/original/image-20170201-12685-525wu2.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=245&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The properties of hydrogen as marked on the periodic table.</span>
<span class="attribution"><span class="source">Shutterstock/duntaro</span></span>
</figcaption>
</figure>
<p>The periodic table is arranged in order of increasing atomic number (left to right, top to bottom). It ranges from element 1 (hydrogen <a href="http://www.rsc.org/periodic-table/element/1/hydrogen">H</a>) in the top left, to the newly approved element 118 (oganesson <a href="http://www.rsc.org/periodic-table/element/118/oganesson">Og</a>) in the bottom right.</p>
<p>The number of neutrons in the nucleus can vary. This gives rise to different isotopes for every element. </p>
<p>For example, you may have heard of <a href="http://science.howstuffworks.com/environmental/earth/geology/carbon-14.htm">carbon-14 dating</a> to determine the age of objects. This isotope is a radioactive version of normal carbon <a href="http://www.rsc.org/periodic-table/element/6/carbon">C</a> (or carbon-12) that has two extra neutrons.</p>
<p>But why is there a separate box of elements below the main table, and why is the main table an odd shape, with a bite taken out of the top? That comes down to how the other component of the atom – the electrons – are arranged.</p>
<h2>The electrons</h2>
<p>We tend to think of atoms as built a bit like onions, with seven layers of electrons called “shells”, labelled K, L, M, N, O, P, and Q, surrounding the core nucleus.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/126483/original/image-20160614-29205-4s6tgg.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/126483/original/image-20160614-29205-4s6tgg.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/126483/original/image-20160614-29205-4s6tgg.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=318&fit=crop&dpr=1 600w, https://images.theconversation.com/files/126483/original/image-20160614-29205-4s6tgg.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=318&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/126483/original/image-20160614-29205-4s6tgg.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=318&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/126483/original/image-20160614-29205-4s6tgg.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=399&fit=crop&dpr=1 754w, https://images.theconversation.com/files/126483/original/image-20160614-29205-4s6tgg.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=399&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/126483/original/image-20160614-29205-4s6tgg.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=399&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Think of the atom with a central nucleus that contains all the protons and neutrons, surrounded by a series of shells that contain the electrons.</span>
<span class="attribution"><span class="source">The Conversation</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Each row in the periodic table sort of corresponds to filling up one of these shells with electrons. Each shell has subshells, and the order in which the shells/subshells get filled is based on the energy required, although it’s a complicated process. We’ll come back to these later.</p>
<p>In simple terms, the first element in each row starts a new shell containing one electron, while the last element in each row has two (or one for the the first row) of the subshells in the outer shell fully occupied. These differences in electrons also account for some of the similarities in properties between elements. </p>
<p>With the one or two subshells in the outer layer full of electrons, the last elements of each row are quite unreactive, as there are no holes or gaps in the outer shell to interact with other atoms.</p>
<p>This is why elements in the last column, such as helium <a href="http://www.rsc.org/periodic-table/element/2/helium">He</a>, neon (<a href="http://www.rsc.org/periodic-table/element/10/neon">Ne</a>), argon (<a href="http://www.rsc.org/periodic-table/element/18/argon">Ar</a>) and so on, are called the <a href="http://www.britannica.com/science/noble-gas">noble gases</a> (or inert gases). They are all gases and they are “noble” because they rarely associate with other elements.</p>
<p>In contrast, the elements of the first column, with the exception of hydrogen (just like English grammar, there’s always an exception!), are called alkali metals. The first-column elements are metal-like in character, but with only one electron in the outer shell, they are very reactive as this lone electron is very easy to engage in chemical bonding. When added to water, they quickly react to form an alkaline (basic) solution.</p>
<p>Each shell can accommodate an increasing number of electrons. The first shell (K) only fits two, so the first row of the periodic table has only two elements: hydrogen (<a href="http://www.rsc.org/periodic-table/element/1/hydrogen">H</a>) with one electron, and helium (<a href="http://www.rsc.org/periodic-table/element/2/helium">He</a>) with two.</p>
<p>The second shell (L) fits eight electrons. Thus the second row of the periodic table contains eight elements, with a gap left between hydrogen and helium to accommodate the extra six. </p>
<p>The third shell (M) fits 18 electrons, but the third row still only has eight elements. This is because the extra ten electrons don’t get added to this layer until after the first two electrons are added to the fourth shell (N) (we’ll get to why, later).</p>
<p>So the gap is expanded in the fourth row to accommodate the additional ten elements, leading to the “bite” out of the top of the table. The extra ten compounds in the middle section are called the <a href="http://www.britannica.com/science/transition-element">transition metals</a>.</p>
<p>The fourth shell holds 32 electrons, but again the extra electrons are not added to this shell until some have also been added to the fifth (O) and sixth (P) shells, meaning that both the fourth and fifth rows hold 18 elements. </p>
<p>For the next two rows (sixth and seventh), rather than further expanding the table sideways to include these extra 14 elements, which would make it too wide to easily read, they have been inserted as a block of two rows, called the <a href="http://www.britannica.com/science/lanthanoid">lanthanoids</a> (elements 57 to 71) and <a href="http://www.britannica.com/science/actinoid-element">actinoids</a> (elements 89 to 103), below the main table.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/154931/original/image-20170131-13243-135rr77.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/154931/original/image-20170131-13243-135rr77.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/154931/original/image-20170131-13243-135rr77.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=359&fit=crop&dpr=1 600w, https://images.theconversation.com/files/154931/original/image-20170131-13243-135rr77.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=359&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/154931/original/image-20170131-13243-135rr77.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=359&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/154931/original/image-20170131-13243-135rr77.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=451&fit=crop&dpr=1 754w, https://images.theconversation.com/files/154931/original/image-20170131-13243-135rr77.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=451&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/154931/original/image-20170131-13243-135rr77.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=451&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The periodic table would look very different if the lanthanoids and actinoids were inserted within the table.</span>
<span class="attribution"><span class="source">The Conversation</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>You can see where they would fit in if the periodic table was widened, if you look at the bottom two squares in the third column of the table above.</p>
<h2>Across the columns</h2>
<p>There is another complicating factor leading to the final shape of the table. As mentioned earlier, as the electrons are added to each layer they go into different subshells (or orbitals), which describes locations around the nucleus where they are most likely to be found. These are known by the letters s, p, d and f.</p>
<p>The letters used for the orbitals are actually derived from descriptions of the emission or absorption of light due to electrons moving between the orbitals: <strong>s</strong>harp, <strong>p</strong>rincipal, <strong>d</strong>iffuse and <strong>f</strong>undamental.</p>
<p>Each shell has its own configuration of subshells named from 1s through to 7p, which gives the total number of electrons in each shell as we progress through the periodic table. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/163552/original/image-20170402-27256-u5wjt7.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/163552/original/image-20170402-27256-u5wjt7.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/163552/original/image-20170402-27256-u5wjt7.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=489&fit=crop&dpr=1 600w, https://images.theconversation.com/files/163552/original/image-20170402-27256-u5wjt7.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=489&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/163552/original/image-20170402-27256-u5wjt7.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=489&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/163552/original/image-20170402-27256-u5wjt7.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=615&fit=crop&dpr=1 754w, https://images.theconversation.com/files/163552/original/image-20170402-27256-u5wjt7.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=615&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/163552/original/image-20170402-27256-u5wjt7.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=615&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption"></span>
<span class="attribution"><span class="source">The Conversation</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>As mentioned earlier the order in which the subshells fill with electrons is not so straightforward. You can see the order in which they fill from the image below, just follow the order as you would read down from left to right.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/163745/original/image-20170403-21969-flm80p.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/163745/original/image-20170403-21969-flm80p.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/163745/original/image-20170403-21969-flm80p.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=353&fit=crop&dpr=1 600w, https://images.theconversation.com/files/163745/original/image-20170403-21969-flm80p.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=353&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/163745/original/image-20170403-21969-flm80p.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=353&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/163745/original/image-20170403-21969-flm80p.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=444&fit=crop&dpr=1 754w, https://images.theconversation.com/files/163745/original/image-20170403-21969-flm80p.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=444&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/163745/original/image-20170403-21969-flm80p.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=444&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption"></span>
<span class="attribution"><span class="source">The Conversation</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>There is an <a href="http://www.ptable.com/#Orbital">interactive periodic table</a> that also illustrates the filling sequence well if you click through the atoms.</p>
<p>Elements within a column generally have similar properties, but in some places elements side by side can also be similar. For example, in the transition metals the cluster of precious metals around copper (<a href="http://www.rsc.org/periodic-table/element/29/copper">Cu</a>), silver (<a href="http://www.rsc.org/periodic-table/element/47/silver">Ag</a>), gold (<a href="http://www.rsc.org/periodic-table/element/79/gold">Au</a>), palladium (<a href="http://www.rsc.org/periodic-table/element/46/palladium">Pd</a>) and platinum (<a href="http://www.rsc.org/periodic-table/element/78/platinum">Pt</a>) are quite alike.</p>
<p>Most of the existing elements with high atomic numbers, including the <a href="https://theconversation.com/the-race-to-find-even-more-new-elements-to-add-to-the-periodic-table-52747">four superheavy elements added last year</a>, are very unstable and have never been detected in, or isolated from, nature. </p>
<p>Instead, they are created and analysed in minute quantities under highly artificial conditions. Theoretically, there could be further elements beyond the 118 now known (there are additional g, h and i suborbitals), but we don’t know yet if any of these would be stable enough to be isolated.</p>
<h2>A classic design</h2>
<p>The periodic table has seen many colourful and informative versions created over the years.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/150468/original/image-20161216-26116-qgzp6m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/150468/original/image-20161216-26116-qgzp6m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/150468/original/image-20161216-26116-qgzp6m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/150468/original/image-20161216-26116-qgzp6m.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/150468/original/image-20161216-26116-qgzp6m.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/150468/original/image-20161216-26116-qgzp6m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/150468/original/image-20161216-26116-qgzp6m.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/150468/original/image-20161216-26116-qgzp6m.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The Periodic table decorates a taxi in the UK.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/gashwin/6959094671/">Flickr/Fr Gaurav Shroff</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
</figcaption>
</figure>
<p>One of my favourites is an <a href="http://www.raci.org.au/periodic-table-on-show">artistic version</a> with original artworks for each element commissioned by the Royal Australian Chemical Institute to celebrate the International Year of Chemistry in 2011.</p>
<p>Another favourite is an <a href="http://www.periodictable.com/index.html">interactive version</a> with pictures of the elements. The creators of this site have also published a coffee table book called <a href="http://www.periodictable.com/Posters/index.theelements.html">The Elements</a> and an <a href="http://www.periodictable.com/Posters/index.theelementsipad.html">Apple app</a> with videos of each element.</p>
<p><a href="http://www.rsc.org/periodic-table">Interactive versions</a> have also been created by the Royal Society of Chemistry (and can also be downloaded as an app) and <a href="http://www.chemeddl.org/resources/ptl/index.php">ChemEd DL</a> among others.</p>
<p>The classic design of the periodic table can be used to play a version of the <a href="http://teachbesideme.com/periodic-table-battleship/">Battleship</a> game.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/118104/original/image-20160411-6250-1lbc5v4.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/118104/original/image-20160411-6250-1lbc5v4.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/118104/original/image-20160411-6250-1lbc5v4.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/118104/original/image-20160411-6250-1lbc5v4.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/118104/original/image-20160411-6250-1lbc5v4.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/118104/original/image-20160411-6250-1lbc5v4.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/118104/original/image-20160411-6250-1lbc5v4.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/118104/original/image-20160411-6250-1lbc5v4.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Playing battleships with the periodic table at the first World Science Festival Brisbane in 2016.</span>
<span class="attribution"><span class="source">The Conversation</span>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
</figcaption>
</figure>
<p>There are also many fun versions created to help organise a multitude of objects, including <a href="http://grafikdzine.deviantart.com/art/Periodic-Food-Table-114678046">food</a>, <a href="http://beergeno.me/wp-content/uploads/2010/10/Per_iodic_Table_Beer_Styles.png">beer</a>, <a href="http://www.fastcocreate.com/3039715/ge-drops-some-social-science-with-the-periodic-table-of-emojis">emojis</a>, <a href="http://ictevangelist.com/wp-content/uploads/2014/07/PTAPPS-ICTEvangelist.png">iPad apps</a> and <a href="http://grosdino.deviantart.com/art/Periodic-Table-of-the-Birds-401058406">birds</a>.</p>
<p>As for Tom Lehrer’s The Elements, the song has yet to be updated to include all the elements known today but it has been covered by other people over the years. </p>
<p>Actor Daniel Radcliffe, of Harry Potter fame, performed a version during a guest appearance on the BBC’s Graham Norton Show.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/rSAaiYKF0cs?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>There are <a href="https://www.youtube.com/watch?v=VgVQKCcfwnU">other musical versions</a> of the elements but they too have yet to be updated to include all entries of the periodic table.</p>
<p>In summary, the periodic table is the chemist’s taxonomy of all elements. Its triumph is that it is still highly relevant to scientists, while also becoming embedded in popular culture.</p><img src="https://counter.theconversation.com/content/52822/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mark Blaskovich receives funding from the Australian National Health and Medical Research Council (NHMRC) and the Wellcome Trust. He is a member of the Royal Australian Chemical Institute and the American Chemical Society.</span></em></p>The periodic table is one of the classic images of science that is found in labs as well as on t-shirts, mugs, even set to music. But what exactly is the periodic table?Mark Blaskovich, Senior Research Officer, The University of QueenslandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/608412016-06-09T17:23:34Z2016-06-09T17:23:34ZIt’s elemental: how to become a periodic table pub quiz champion<figure><img src="https://images.theconversation.com/files/125971/original/image-20160609-7049-130dk32.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">What's in a name?</span> <span class="attribution"><a class="source" href="http://www.shutterstock.com/dl2_lim.mhtml?src=gb4wr4jug4vndzUhvhIPbg-1-9&clicksrc=download_btn_inline&id=369111563&size=medium_jpg&submit_jpg=">Shutterstock</a></span></figcaption></figure><p>With the naming of <a href="https://theconversation.com/four-new-elements-named-heres-how-the-periodic-table-evolved-60276">four new chemical elements</a>, it’s worth reflecting on their <a href="http://www.nndc.bnl.gov/content/elements.html">long and interesting history</a> – and you can become a pub quiz champion on the topic in the process. Indeed, while the periodic table may sound like a rather dry topic, it’s actually a subject packed full of the weird and wonderful.</p>
<p>The concept of discrete atoms was proposed by Robert Boyle in 1661, but in the first chemistry textbook, Traité élémentaire de chimie, published in that portentous, revolutionary year of 1789, <a href="http://gallica.bnf.fr/ark:/12148/btv1b8615746s/f15.image.r=.langEN">Antoine-Laurent de Lavoisier</a> listed a number of the chemical elements, including 27 known today. They included hydrogen, nitrogen, oxygen, phosphorus, sulfur, iron, zinc, mercury and gold.</p>
<p>Not that it did him any good. Lavoisier was guillotined during the Reign of Terror in 1794, the judge allegedly commenting <a href="https://www.acs.org/content/dam/acsorg/education/whatischemistry/landmarks/lavoisier/antoine-laurent-lavoisier-commemorative-booklet.pdf">“La République n'a pas besoin de savants ni de chimistes”</a> (“The Republic does not need scientists or chemists”).</p>
<p>It was Lavoisier’s contemporary, <a href="http://www.britannica.com/biography/Nicolas-Louis-Vauquelin">Louis Nicolas Vauquelin</a> who not only discovered the element <a href="http://www.rsc.org/periodic-table/element/4/beryllium">beryllium</a> in 1798 but also in 1803 synthesised the oxide of another new element. Finding it to be volatile, he gave it the baffling name “ptene”, derived from the Greek word for winged. Fortunately for posterity, this element is now known as <a href="http://www.rsc.org/periodic-table/element/76/osmium">osmium</a> (from the ozone-like smell of the oxide) and so far, no unpronounceable name has been adopted for any element.</p>
<h2>118: the magic number?</h2>
<p>Since the start of the 19th century, the number of known elements has steadily risen, reaching its present total of 118. <a href="http://www.world-nuclear.org/information-library/nuclear-fuel-cycle/introduction/what-is-uranium-how-does-it-work.aspx">Uranium</a> (number 92) is the heaviest element present in the Earth in an appreciable amount and all successive elements have been made in scientific laboratories. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/125972/original/image-20160609-7059-hru8f8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/125972/original/image-20160609-7059-hru8f8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=464&fit=crop&dpr=1 600w, https://images.theconversation.com/files/125972/original/image-20160609-7059-hru8f8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=464&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/125972/original/image-20160609-7059-hru8f8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=464&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/125972/original/image-20160609-7059-hru8f8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=583&fit=crop&dpr=1 754w, https://images.theconversation.com/files/125972/original/image-20160609-7059-hru8f8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=583&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/125972/original/image-20160609-7059-hru8f8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=583&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Nagasaki: the dark side or uranium.</span>
<span class="attribution"><a class="source" href="http://www.shutterstock.com/dl2_lim.mhtml?src=C6hNLn0UwzAfUtvW1n9kEA-1-6&clicksrc=download_btn_inline&id=251930701&size=medium_jpg&submit_jpg=">Shutterstock</a></span>
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<p>The International Union of Pure and Applied Chemistry (IUPAC) has proposed names for <a href="http://iupac.org/cms/wp-content/uploads/2016/06/Press-Release_Naming-Four-New-Elements_8June2016.pdf">four recently synthesised chemical elements</a>, which complete the Periodic Table up to and including element 118.</p>
<p>Until now, this quartet have been known by their atomic numbers of 113, 115, 117 and 118 – or the temporary names of ununtrium (symbol Uut), ununpentium (Uup), ununseptium (Uus), and ununoctium (Uuo) respectively. The proposed names now are respectively nihonium (symbol Nh), moscovium (Mc), tennessine (Ts), and oganesson (Og).</p>
<p>Most elements have names ending in “–ium”. All but one of those are metals or metalloids; the one exception being <a href="http://www.rsc.org/periodic-table/element/2/helium">helium</a>, first discovered in the sun’s spectrum in 1868 and given its name from the Greek word for the sun – ἥλιος (helios) – before helium was identified on Earth (1895) and the character of the element could be known.</p>
<p>Two of these new elements are given names ending in –ium, though no one yet knows if they are metallic or not; the names of the other two are given endings appropriate to their positions in the Periodic Table. Tennessine is assigned to Group 17 (VIIB), together with the halogens fluorine, chlorine, bromine, iodine and astatine. Oganesson is in Group 18 (0), together with helium, neon, argon, krypton, xenon and radon.</p>
<p>The right to give a name to a newly discovered element is prestigious and has traditionally been seen to be in the hands of the discoverers. Four countries have contributed to the discoveries of new elements during the past half century. The work of the <a href="https://www.gsi.de/en/start/news.htm">German GSI Helmholtz Centre for Heavy Ion Research</a> at Darmstadt in discovering elements 107-112 – bohrium, meitnerium, hassium, darmstadtium, roentgenium and copernicum (as well as important confirmatory work on other elements) – is commemorated in their names. </p>
<p>As the leading German researcher Sigurd Hofmann <a href="http://www.popsci.com/scitech/article/2009-06/whats-it-name-element-periodic-table">commented</a>: </p>
<blockquote>
<p>We are being very democratic about naming. We are very careful, because these names last forever. We want the name to make sense now and forever – a famous scientist, famous lab, maybe a Greek philosopher.</p>
</blockquote>
<p>So don’t expect Boaty McBoatfacium just yet.</p>
<h2>What’s in a name?</h2>
<p>Of the four newest elements, two names are linked to Russia, one to Japan and one to the US, reflecting the international nature of the synthesis of these new man-made elements. But things have not always been like that.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/125973/original/image-20160609-7049-y0fkh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/125973/original/image-20160609-7049-y0fkh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/125973/original/image-20160609-7049-y0fkh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/125973/original/image-20160609-7049-y0fkh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/125973/original/image-20160609-7049-y0fkh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/125973/original/image-20160609-7049-y0fkh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/125973/original/image-20160609-7049-y0fkh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">And I shall name it…</span>
<span class="attribution"><a class="source" href="http://www.shutterstock.com/cat.mhtml?lang=en&language=en&ref_site=photo&search_source=search_form&version=llv1&anyorall=all&safesearch=1&use_local_boost=1&autocomplete_id=&search_tracking_id=xnKAk0SAZ3_s0PwAjcsWUw&searchterm=chemical%20elementts&show_color_wheel=1&orient=&commercial_ok=&media_type=images&search_cat=&searchtermx=&photographer_name=&people_gender=&people_age=&people_ethnicity=&people_number=&color=&page=1&inline=321825182">Shutterstock</a></span>
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<p>Originally, this kind of nuclear synthesis was only carried out in the US at the <a href="http://www.berkeley.edu">University of California, Berkeley</a>, between 1940 and 1955, so they gave names to elements 93 (neptunium) to 101 (mendelevium). But the discovery of the next few elements was dominated by controversy, as both American and Soviet researchers were active, both schools claiming priority in discovery. The <a href="http://cenblog.org/newscripts/2011/08/whats-in-a-name-for-chemists-their-fields-soul/">Transfermium Wars</a> had begun, and it was not until the beginning of a new millennium that these names were sorted out by an <a href="http://www.degruyter.com/dg/viewarticle.fullcontentlink:pdfeventlink/$002fj$002fpac.1997.69.issue-12$002fpac199769122471$002fpac199769122471.pdf/pac199769122471.pdf?t:ac=j$002fpac.1997.69.issue-12$002fpac199769122471$002fpac199769122471.xml">international committee</a>.</p>
<p>Happily, international teams now work together to discover new chemical elements. Discoverers have often named a new element after their country, as with polonium (by Marie Curie) and americium, for example. Nihonium isn’t the first time that an element has taken its name from Japan. In 1909, the Japanese chemist Masataka Ogawa thought he had discovered element 43, and suggested that it be called <a href="http://pubs.acs.org/doi/abs/10.1021/ja01942a006">nipponium</a>.</p>
<p>But he hadn’t, so it wasn’t; we now know element 43 as technetium and it was not discovered until 1937. But it looks as if Ogawa had discovered a new element, rhenium, which was not recognised by others <a href="http://www.sciencedirect.com/science/article/pii/S0584854704001065">until 1925</a>.</p>
<h2>The whirligig of time</h2>
<p>Indeed, over the past centuries, many claims have been made in error for the discovery of elements; in most cases these have been <a href="http://www.rsc.org/chemistryworld/2015/02/lost-elements-periodic-table-shadow-side">innocent mistakes</a>, but a 1999 claim for the synthesis of elements 116 and 118 is now recognised to have involved fraud on the part of one of the <a href="http://physicsworld.com/cws/article/news/2001/aug/02/element-118-disappears-two-years-after-it-was-discovered">scientists involved</a>.</p>
<p>Not the least achievement of those who name compounds has been to set right historical injustices. <a href="http://www.atomicarchive.com/Bios/Meitner.shtml">Lise Meitner</a> was along with her colleague Otto Hahn a co-discoverer of <a href="http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa_pre_2011/radiation/nuclearfissionrev1.shtml">nuclear fission</a>, but did not share the award of the 1944 Nobel Prize in Chemistry for this; it went solely to Hahn. </p>
<p>In 1994, however, IUPAC recommended the adoption of the names hahnium and meitenerium for elements 108 and 109 respectively, commemorating them both. In the event, element 108 was named hessium, but element 109 was officially named meitnerium.</p>
<p>As Feste remarks in Twelfth Night, “And thus the whirligig of time brings in his revenges.” </p>
<p>All you have to do now is start revising.</p><img src="https://counter.theconversation.com/content/60841/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Simon Cotton does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>As four new chemical elements are named, here’s all you need to know.Simon Cotton, Senior Lecturer in Chemistry, University of BirminghamLicensed as Creative Commons – attribution, no derivatives.