Happy 150th birthday to the periodic table

A century and a half ago, Dmitri Mendeleev published an organisation of the elements that had been discovered at that point. His chart made sense – listing the elements in order of increasing atomic mass, looping to a new list when their properties started to repeat. Most importantly Mendeleev left empty spots where things didn’t match up - he anticipated elements that were yet to be found or made and properties that had yet to be understood, pointing other scientists towards new discoveries.

This year, the periodic table of the elements celebrates its 150^th birthday. It’s grown up a lot in that time. It’s more colourful, it’s got fewer holes, and it is one of the most easily recognised shapes in the world. It’s more than recognisable, though – it represents the vastly creative and collaborative nature of science in a way that few other icons do.

You see, expanding the periodic table is no small feat. Making a new element takes bashing together other atoms at just the right (incredibly high) speed. Too slow and the atoms won’t stay together, too fast and they’ll smash each other apart. Just getting the collision to happen at all is tough enough, but even then, the new element (known as a superheavy element, or SHE, after their huge atomic mass) might only exist for a fraction of a fraction of a second (10^-4 seconds, according to eminent theorist John Wheeler).

The last batch of four new elements, accepted by the International Union of Pure and Applied Chemistry (IUPAC) in 2016, was the work of over a hundred scientists in four separate teams over countless hours. This is demanding stuff, but whatever new elements we find don’t have immediate applications. We really must ask (don’t panic): why bother?

Curiosity suffices for some. Sigurd Hofmann, a giant of SHE discovery who has contributed to the creation of eight new elements (so far), describes the “sense of excitement which has motivated workers in this field” in his 2002 book On Beyond Uranium: Journey to the End of the Periodic Table.

That’s not all. As we strive to find new elements, we unlock more and more information about the physics at the smallest of scales. Superheavy elements are so heavy that they start to show all sorts of wacky behaviour. In particular, their electrons move much faster than those of lighter elements, so that relativity starts to play an important role. At this scale, the quantum and relativistic behaviour of SHE might point us towards answers to some of the big questions in theoretical physics.

“But Clare,” I hear you cry, “Science must have practical value! Personal fulfilment and theoretical answers are nice, but there are so many problems, and only so much money!” Absolutely. But consider this: when americium was created in 1944, we did not yet know that it would be a key component in smoke detectors, which save thousands of lives each year. It is possible that superheavies in the fabled “island of stability” could be solutions to problems we don’t even know exist yet.

In the same way that Mendeleev left gaps in his periodic table, anticipating future discoveries without knowing the solutions they might bring, we should be comfortable with reaching into the scientific unknown without an immediate motivation. This isn’t just knowledge for knowledge’s sake - this is science, saving the world without knowing it yet.

Want to know more about…

• The periodic table? Check out IUPAC’s page about this amazing chart or take the IUPAC Periodic Table Challenge.
• How new elements are made? Check out these articles that go into more detail than this one:
  - Making New Elements
  - Smashing new elements into existence gets a lot harder from here
  - Quest for superheavy nuclei (more advanced).