Dr Ben Pilgrim, University of Cambridge
Most school science labs have a periodic table on the wall but until now, there have been a few missing elements towards the bottom. Ben Pilgrim explained to Kat Arney why everyone is suddenly very excited about this historic table...
Ben - Yes, there's been a very exciting week for chemistry. So IUPAC (The International Union of Pure and Applied Chemistry), announced that four elements (elements number 113, 115, 117 and 118) have been discovered. Now these haven't all been discovered in the last few days - that would be quite a coincidence. It's actually been about 10 or 15 years since scientists first started gathering evidence to suggest that these elements did exist. So there have been gaps in the periodic table; they've been predicted to be there for a long time, but it's all about the scientists getting enough data to be able to be sure that these elements are actually there.
Kat - The periodic table - a lot of people have heard of it, a lot of people probably recognise it. What exactly is it as a way of categorising elements? How did they know that there were these gaps in there?
Ben - So, elements are placed in a periodic table depending on the number of protons, which are a particle found in the nucleus of every atom, and there's basically, you know, the first element hydrogen has one proton, the second element helium has two, and so on. The number of protons defines what element you have and, it so happens these numbers I said earlier, they are the number of protons that we hadn't found yet but, you know, they should be there because it should be possible to have one with that particular number.
Kat - So how do you go about discovering a new element - I assume you don't find it down the back of the sofa?
Ben - Yes, I mean the problem is that there's about 90 elements on the earth, sort of naturally occurring, we find them around. They might be bound up with other things but they will always be there, they're stable. An oxygen will always be an oxygen, a gold will always be a gold. The trouble with these elements is they're radioactive, they're unstable. They fall apart after a very short amount to time - sometimes fractions of a second, and so the scientists actually have to make them and they do this by firing two lighter elements at each other. So, for example, they fire a calcium atom at an atom of americium. Calcium has a number of 20 and americium has a number of 95 and that adds together to make 115. Part of the difficulty is that these new ones we make, they are unstable, they fall apart, so how do we know we've made them?
Chris - They hand around for something in the region of about a microsecond through to a couple of seconds, don't they. I mean someone was saying that one of these new elements, they'd only ever made 90 atoms ever.
Ben - Yes. One of the ones I found out that 117 apparently 15 atoms have been observed, so...
Chris - As many as that.
Ben - You don't want to...
Kat - Don't spend them all at once.
Ben - You don't want to go to the toilet and miss it or something, do you? But, imagine if you had a video, for example, of a game of snooker and someone had, by some computer wizardry, removed the cue ball from the piece of videotape that you might be able to think about where the cue ball was based on what the other balls were moving and how they were moving around the table,and that's a bit like what they have to do here. They have to kind of use what these heavy atoms decay into, and then kind of reconstruct and then assume what they had before.
Chris - Can I just ask you the really simple question though which is - why are we doing this?
Ben - Well I think it's very exciting because there's something that's referred to as the 'island of stability'. So, as we get heavier and heavier, the atoms are becoming less stable but, it's been hypothesised by a number of people that, once we get a little bit higher up we might actually get back into some stable elements again, some stable atoms and these may have new properties that, you know, haven't been seen before. So that's very exciting.
Kat - And, of course, the big question is - what are we going to call them, because numbers aren't cool? We need like brilliant names. What's the...
Chris - Ununtrium and ununpentium and ununseptium. Is that not sexy enough?
Kat - Come on, no!
Ben - Those names are a little dull, so they can be called after a number of things. A number are called after countries or places or after famous scientists.
Chris - There was a petition this week to call one after Lemmy from Motorhead.
Ben - Yes, this would be one of the heaviest of the heavy metals. Unfortunately, I think it has to be a scientist, according to the rules. There are certainly some British scientists - Humphry Davy, Michael Faraday that don't have elements named after them. Even perhaps one of our most famous scientist overall, Isaac Newton, doesn't have an element. But because the research groups - 113 was discovered by a Japanese group, the others by a collaboration between Russian scientists and American scientists, I think we might maybe see a reference to Japan in one of them, one based on the name of Moscow I've heard, and so I think that's perhaps slightly more likely.
Kat - Well, I think we shall have to see.