Just before the New Year, science welcomed four new elements to the periodic table. It’s kind of a big deal, but we’ll have to get geeky to explain why.
The new elements are Numbers 113, 115, 117 and 118. The numbers refer to the number of protons in the nucleus of the element. For now, the elements have placeholder names that are simply a pseudo-Latinized version of their number. Element 118 is temporarily known as ununoctium; one-one-eightium, as it were. The naming process for new elements is unbelievably complex. It can take years to settle on a name. But that’s not what WC wants to talk about.
You can see that the four newest members of the periodic table completed the seventh row, called the seventh period in chemistry-speak. The next new element will start a new row or period. And it may be an element that hangs around long enough to be useful. You see, all of the elements since Element 95, Americium, don’t occur in nature; all of them are synthesized1. Scientists slam tiny bits of other elements into each other at near light speed to make an atom or two of the these manmade elements.
Now before you get snooty about these arriviste, manmade elements, remember all elements are the result of one kind of explosion or another.2 The Big Bang produced Hydrogen and Helium, and tiny amounts of Lithium and Beryllium. Another kind of explosion, the fusion process that powers stars, makes a whole bunch of elements, up through Element 26, Iron, and possibly a few more. When big stars explode in a supernova, a really, really big explosion, more elements up through at least Element 92, Uranium, get made. And when cosmic rays collide with the nuclei of some of the higher-numbered elements get made as well. Mankind is just extending the tradition by which a chunk of the Universe was made when they bang particles together really fast.
Most of the transuranic elements have half lives measured in mere minutes, seconds or even milliseconds. For the last half dozen or so elements, only a very few atoms – not grams, milligrams or micrograms; individual atoms – have been produced. When you smash a Calcium ion into a Curium ion too softly, it just bounces off. If you hit it to hard, they blow each other apart. Scientists have to find the sweet spot; that’s difficult.
With each step up the periodic table, you are cramming more protons and neutrons into the nucleus. Protons repel each other – positively charged particles, right? The neutrons – particles that don’t have an electrical charge – supply the strong nuclear force that glues the proton together. But too many protons and neutrons crammed in to one place is inherently unstable. Hence, the very short half lives of these new elements. Even worse, each proton has to have a balancing electron in the shell surrounding the nucleus. Electrons pack themselves in to shells, and for these new elements there are so many shells that the outermost electrons are moving at nearly light speed. So you get weird, relativistic effects as well. So the cumulative effects are about as stable as Newt Gingrich (Gingrichium?), and blow themselves apart – the technical term is “decay” – into other elements almost immediately.
When WC was studying chemistry, in the early 1970s, there were 101 elements in the periodic table. So, see, progress! But join WC in welcoming Ununtritium, UnunPentium, Ununseptium and Ununoctium to the Periodic Table of the elements. It may be a while before we see Ununennium and Unbinilium (elements 119 and 120). So enjoy the thrill.3 4
- Any completely naturally occurring Americium on Earth would have vanished a long time ago, decaying into other elements. The longest know half-life of an Americium isotope is about 7,370 years. It all would have decayed before the earth cooled. But nuclear bombs, nuclear reactors and other man-made processes produce the stuff, so it does occur in nature again. ↩
- Remember, too that ordinary matter, the elements, accounts for only about 15% of the stuff in the universe. The rest is dark matter, or maybe dark matter and dark energy. Science doesn’t have a clue what that stuff is yet. ↩
- WC promises to avoid extreme technogeekery the rest of the week. ↩
- Yes, chemistry majors, this article contains gross oversimplifications. ↩