Nowadays, it is an incredible tool for chemists around the world as they experiment with many elements and constantly attempt to create new ones. There have been many changes in the periodic table since, most notably the addition of a whole new column (the Noble Gases) by William Ramsey, leaving him with the 1904 Nobel Prize3 . Mendeleev wasn’t able to predict the existence of column 8 as he focused on elements that formed compounds in his table and considered the noble gases to have extremely low reactivity since they already have a full outer shell (3). 

Furthermore, it is hypothesized that atoms are limited up to 172 protons when forming a nucleus that will stay together (4) . This is because atoms beyond that limit may be capable of summoning electrons from space.(5) However, this is only a theory, and as Witold Nazarewicz, a Polish physicist says: “We really do not know what is the heaviest element that could exist,(6)”.

Oganesson is Element 118, named after Yuri Oganessian in 2016.(7) At a similar time frame to the discoveries 115, 117 and 113, Oganesson emerged.  All four of these elements are known as superheavy elements because they have an atomic number greater than 103, with 118 being the highest; it makes sense for it to behave differently. Oganesson has an estimated half-life of less than 1ms (8) , meaning it is unrealistic to analyze or experiment on as it is radioactive and therefore extremely unstable. This is common in many elements with large atomic numbers, due to how unstable the nucleus is.

Therefore, researchers need to use atomic calculations for these kinds of elements. So imagine the surprise when Paul Jerabek and Peter Schwerdtfeger (from Massey University, NZ) and his team used Fermion localization to discover that Oganesson’s electrons and nucleons had a uniform distribution. (9)

But what does this mean? Excellent question, not so excellent an answer. This demonstrates that elements begin to (in colloquial terms) defy expectations and ‘break physics’. So in my previous point, when I said that element would have to be able to summon electrons from space, that is possible. Element 118 marks the end of Mendeleev’s periodic table, every space filled, and simultaneously ruins it.

And now to counter this: Accelerator experiments disagree, saying that the Periodic Table can fit rows up to Z (atomic number) =172.(10) This counter may seem like an issue, but if you think further, although Mendeleev’s periodic table can fit these elements, it really shouldn’t. A new period (row) could be created underneath the Periodic table, as the number of shells and electrons in the outer shell rule would still work, but it would ruin the most useful part of the periodic table. The beauty of the standard periodic table is how it can accurately predict the behaviour of elements, but these superheavies won’t have similar characteristics. So even though they can fit, it will ruin what makes Mendeleev’s table so important. 

To conclude, my answer is yes. Mendeleev’s periodic table is finished, and we will finish a more inclusive periodic table someday, as we are increasingly stepping forward, embracing new technologies and discoveries every day we may even find a way to rearrange the periodic table. Apart from that, our time is infinite (technically and as far as we are aware) and elements are likely not, as evidenced by the fact that an element with over 173 protons will most likely not be able to exist. Overall, elements with atomic numbers over 118 have no more space on Mendeleev’s periodic table. Its separation based on characteristics no longer applies for the superheavies, leaving us with a much different question: not when will the periodic table finish, but who will design our next one? With our generation becoming adults, us children equipped with technology and knowledge never seen before, who will be the one whose name future schoolchildren will memorise? Who will be the creator of the newest periodic table?