Mark called the show to ask how many elements there are in the periodic table, and whether it had changed since he was at school, 40 years ago.
Ewen Kellar answered Mark's question
Ewen - Right. I think there's something like 114 now I think. There's a number of synthetic elements which have incredibly transitory lives of trillionths of a second which are more sort of sparkles in a theoristís mind rather than in reality. But in various nuclear reactors and a Large Hadron Collider and similar instruments, they have succeeded in literally forcing the building blocks of atoms, nuclei where youíve got protons and neutrons, and electrons together to form atoms which are ridiculously heavy. So they're at the far end of the periodic table, which will literally hold together for virtually no time at all before they fall apart because basically, they're just too unstable to hang on in there. But the number of stable elements will not have changed since you were doing your work. Though I do believe there are some theoreticians who think that there are some super heavy atoms which theoretically would be stable. But they just havenít managed to build them up yet to see whether they will work. But you never know in the future. They might exist.
Chris - These are so-called islands of stability, arenít they? The idea being that at the moment, these things donít hang around for very long but if we could make something of the right sort of size then it will hang around for long enough and it will act as a stepping stone that we can then use to get to even bigger elements which will have all kinds of exciting properties because we donít know what these things might behave like. We might be able to make exciting things out of them that would do exciting jobs that the elements we currently are endowed with on earth can't do.
Ewen - I do confess, I've just gone and checked online. Itís actually 118 according to the periodic table now.
Chris - And I hope, with a slightly more imaginative name, unundecium, which number 112 had to live with for a little while until they came up with something a little bit better for it.
Ewen - Yeah. Well at least itís not unobtanium.
Chris - Which is kind of possibly where we are next! Mark, great question. Thank you very much.