Monday, March 11, 2013

Element of the Month: Seaborgium!

March's Element of the Month:


Atomic Mass: 269 amu or thereabouts
Melting Point: no tellin'
Boiling Point: no tellin'

Our Element of the Month for March is Seaborgium, Element 106, and you have probably already guessed from that number that it is a very fakey Element indeed. It was brought into being in 1974 by the University of California Golden Bears, and named in 1997 after a long and boring controversy about whether it was OK to name an element after a living person whose name wasn’t “Einstein.”

As an aficionado of IAT Elemental reportage, you doubtless expect me to natter on at this point about half-life and how quickly Seaborgium will change into something else. Well: no more than 130 seconds, and Rutherfordium. But let’s take on something a little more challenging: WHY do the fakey Elements (and some of the real ones) have this weird tendency to decay? Why do Elements, which are supposed to be so… so… elemental, play this trick of shedding pieces and transforming into something else?

It turns out that this is a damned difficult question to get a straight answer to.  Or, it is for me at least, using the wiki and my modest Google-fu. It might be that everybody learns the answer in junior high science class these days, and it’s so obvious that nobody has bothered to write it down. But I really had to dig, and even at that I’m not 100% sure I’m getting it right.

What seems to happen is a nucleus gets too big to hold itself together. So, let’s start with what holds a nucleus together in the first place – ladies and gentlemen, give it up for the NUCLEAR FORCE. The Nuclear Force (which, mind you, turns out to be a simplified notion of a bunch of other stuff going on at the subatomic level) is broadly analogous to gravity, in that it holds protons and neutrons together pretty tightly when they are close to each other but diminishes quickly as they get further away from each other.

Meanwhile, you’ve also got the Electrostatic Force at work. This is the force that makes similarly charged particles repulse each other, broadly analogous to what happens when you try to push the same sides of a magnet together. Since neutrons are neutral (hence the name) and protons are positive (hence the name, or as good as), all you’ve got in a nucleus electrostatically speaking are positive charges, all of which are a little uncomfortable with each other.

The Centerfold!

If you've been paying attention, you'll realize that there can't be a centerfold
for Seaborgium, so here is a cute kitten instead.  If you are curious why there
can't be a centerfold for Seaborgium, or you would like to express an opinion
regarding the cuteness of the kitten, please do so in the comments.
In most real Elements – let’s take Cobalt, with its 27 protons and 32 neutrons – the nucleus is small enough that the nuclear force holding the 59 “nucleons” together overcomes the electrostatic force pushing the 27 protons away from each other, and you’ve got a nice, happy, non-radioactive atom.*

But what about a fakey Element like Seaborgium? 106 protons (hence the atomic number) and, depending on the recipe that was used to make it, somewhere between 159 and 165 neutrons. Your first thought might be that all those nucleons thrown in together would generate a ton of nuclear force glue. But remember, the nuclear force diminishes very rapidly as particles get further apart. So, although all those protons and neutrons are holding onto their immediate neighbors for dear life, the ones at the outer edges have very little “pull” – literally – with their colleagues on the other side of the cluster. Meanwhile those 106 positive electrostatic charges don’t decrease nearly so much with distance, and each one proton is just itching to get the hell away from its 105 annoying peers. And this is why, if you had a (UnitedStatesian) ton of Seaborgium at noon, you’d only have .0000298 of an ounce left when you got back from lunch at 1 p.m.

What generally happens with Seaborgium in particular is “alpha decay,” in which two protons that are still on speaking terms leave together, taking two neutrons with them in a kind of sub-atomic double-date. What happens to this “alpha particle”? I’m not sure, although it seems that some of them acquire electrons somehow and become respectable Helium molecules. Meanwhile, the Seaborgium (Element 106) has lost two protons and becomes Rutherfordium (Element 104). The Rutherfordium will of course be too big to cohere properly, and will promptly decay into something else: Curium, or Californium, or Dubnium, or boring old Plutonium. But only for a while.

* Incidentally, the threshold at which a nucleus will remain stable is extremely narrow. Remember nice, stable Cobalt, with 27 protons and 32 neutrons? If you make fakey Cobalt by taking away 1, 2, or 3 neutrons, you don’t have enough nuclear force to combat the electrostatic force, and your atom is radioactive, on the way to being Iron with a half-life of less than a year. Add a neutron, and you’d expect to be good – except now you’ve made the nucleus too big, and therefore too spread out, to overcome the repelling force of its protons. It will be radioactive, turning into Nickel with a half-life of five years. Nature’s got rules, and nature’s got laws.


Michael5000 said...

I forgot to credit Morgan for peer review of this article.

Yankee in England said...

I a curious how you acquired the cute kitten photo? It it your kitten, a friends kitten, a random photo of a kitten from Google images?

Michael5000 said...

It is a random photo from the internet.

No, wait, it's an old picture of the late Glen Seaborg's cat "Schroedinger," when he was a kitten.

gl. said...

the periodic table of kittens could really be a hit.

Michael5000 said...

What determines the Kittenic Number?