Element 118, the final element in our International Year of the Periodic Table series, is oganesson. Oganesson was discovered in 2002 and its properties defy our expectations based on trends in the periodic table.

Oganesson has several distinctions amongst all of the elements in the periodic table. Firstly, it’s the only element named after someone who’s still alive. It’s named after Yuri Oganessian, the Russian-Armenian physicist who’s considered to be the leading researcher in the world when it comes to making superheavy elements. Secondly, it’s currently the heaviest element we’ve managed to make. Though scientists are working to try and make heavier elements, so far they’ve yet to succeed.

Another of oganesson’s distinctions is that it’s one of the periodic table’s weirdest elements – based on predicted properties, at least. It’s a member of the noble gas group of elements, which should mean it’s (as the name suggests) a gas at room temperature, and fairly unreactive. However, calculations suggest it should be a metallic semiconductor, making its properties distinctly different from the other elements in its group.

This has resounding implications for the periodic table. Part of the genius of its design is the way in which elements with similar chemical properties are grouped together. In the past, chemists were able to use the properties of elements they knew to predict the properties of the elements they’d yet to discover, based on their position in the periodic table. If newer elements don’t fall in line with the properties we might predict from the periodic table, then it loses its predictive power for these and subsequent elements.

At present, some might see this as something of an irrelevance. The superheavy elements, like oganesson, which start to diverge from the periodic table’s usual trends, are only made in minute amounts. Only a few atoms of oganesson have ever been made, so it’s not likely that we’ll ever produce enough of it for its properties to be anything more than a passing curiosity.

Oganesson is the heaviest element known to date. However, it’s possible we could still discover more elements in the future. Indeed, scientists already kicked off the hunt for element 119. While these elements are likely to be just as fleeting, it’s also theorised that an ‘island of stability’ exists for isotopes of some superheavy elements. These isotopes could be much longer-lived than those currently produced, making more detailed study of these elements possible.

The periodic table is complete, for now, in its neatest form – all seven periods of elements currently known are filled. When element 119 is discovered, it’ll be the first element in period 8, a period which will likely never be completed. And with it likely that we’ll see longer and longer between new element discoveries, it’s unlikely that we’ll see many more new additions in our lifetimes.

But what I hope that this series has shown is that we don’t need new elements to keep the periodic table interesting. Each of the elements has its own particular character, its own backstory, its own catalogue of uses. And all of these are in constant flux – we make unexpected discoveries about the properties of existing elements, their uses change over time as we learn more about their dangers, limitations, or capabilities, and their stories continue to grow. The periodic table is a library of 118 fascinating chemical stories – and all 118 are still being written.

Remember, you can keep track of all of the previous entries in this series on the site here, or on the Royal Society of Chemistry’s dedicated page.

You can now download all 118 element graphics here.

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