Elements of the future
What might elements, and the periodic table, look like in the future? Katie Haylor spoke with Kit Chapman, author and comment editor for Chemistry World magazine, and author of Superheavy: making and breaking the periodic table. First up, Katie asked, is there actually space for more elements in the table?
Kit - There's lots of space, don't worry about that at all. At the moment two groups are even working to try and get the next two elements and they're actually in a race at the moment in Russia and Japan. So we're expecting that there's gonna be another two elements hopefully within the next five years.
Katie - Now, are these man-made elements?
Kit - Almost certainly. So they don't necessarily have to be. There are theories saying that you could find those elements on Earth, some of them. But at the moment all the elements we're discovering past uranium, which is element 92, have been first discovered by a man-made project. And so these elements are probably going to be found in particle accelerators and we are going to be making them a single atom at a time.
Katie - So if you're hinting that there may be some naturally occurring ones we just haven't found yet, where might they be? Haven't we looked in lots of places?
Kit - That's a very good question. And we have looked everywhere! In the 1970s we looked in the BART system, that's a tube system in San Francisco, we looked in salt mines, we even looked in churches because there was a theory that you could find it in the lead lining of stained glass windows and you could find traces of those super-heavy elements as we call them. But so far we've not found anything. There was a group from Israel that claimed they found element 126. Again that's never been proven. But in theory there could be some of those elements and this is because of something called magic numbers. So we talk about electrons having shells for atoms. There's a good theory put forward by someone call Maria Goeppert Mayer that neutrons and protons also have these magic numbers of shells and that balances everything out and makes them much more stable. Now these elements that we're finding at the moment, the ones we're making, they last very, very small amounts of time. So element 118 for example lasts less than a thousandth of a second, it’s seven ten thousandths of a second.
Katie - Wow, okay. I'm just trying wrap my head around that! So talking about making new elements, can we just cycle back to how you actually do that?
Kit - Yeah sure. So there are two ways you can do it. The first ones past uranium were made through essentially what we now use as nuclear reactors. So it's something called neutron capture and the idea is that you bombard something with neutrons and through radiation, something called beta radiation, neutron turns into a proton and you move one place up the periodic table. These days we've got a particle accelerator. So you get a giant magnet and you make ions - that's a nucleus of an element like calcium for example, that's element 20 - and you make it go faster and faster and faster and you fire it as fast as you can at a target. And if you collide with a nucleus usually it explodes in something called fission. That's not what we want. What we want is fusion, where the nucleus sort of gloops together and forms a larger atom.
Katie - Is there an upper limit to how many we can make?
Kit - Well we don't know. We think the upper limit is about element 172 or 173, before everything will just become too unstable. So that means we haven't found around a third of the elements that could exist.
Katie - Wow. So there's there's a lot to keep chemists busy!
Kit - There's a lot to keep chemists busy and physicists because it gets really weird as well. Because we're making these things bigger and bigger and bigger, we start getting something called relativistic effects. And that's like Einstein in the theory of relativity. It starts affecting how the electrons behave and things get very, very weird. We could have nuclei is that twist into the shape of a doughnut so there's a hole in the middle. We could see electrons orbiting through the nucleus. And so all of this means that the periodic table gets very, very weird indeed.
Katie - So how weird do you reckon it's going to get? How far are we going to stray?
Kit - It's possible that there might be an area where chemistry just simply does not work. The elements become so strange that they would exist as cations only, as we call it, so it wouldn't be able to attract electrons. Very, very strange! At the moment, with element 118 we're already seeing that weirdness. So earlier we were speaking about how elements in groups have different properties as they go down. Element 118, oganesson, is in theory a noble gas. It should be a gas at room temperature, it shouldn't react very much with elements at all. Oganesson however, we think is very reactive and is actually a solid at room temperature, so it just stops following the rules completely.
Katie - So potentially new discoveries may well break the periodic table.
Kit - We might already have broken the periodic table!