h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

So how do you change an element? Is it radiation ?(Jemima tries to be clever and falls short of the mark) You said it's hard but exactly how do you do it? Do you need a lot of heat? Please explain in words of one syllable for the people who got 58% in their physics exam!!
Jem

There are a few different ways, but they all involve a lot of energy...

Nuclear fission - the process used in all nuclear power stations, and the first nuclear weapons - is basically taking a heavy element (like uranium) and having it break down into two lighter elements.

When it does so, it gives off spare neutrons.

In a small lump of uranium, these spare neutrons mostly just fly off. But if the lump is big enough, they hit other uranium atoms, and cause them to split. If the lump is JUST large enough, there are just enough neutrons being produced to make sure that the process is self-sustaining - a chain reaction. If the lump is too big, it goes CRITICAL, and there reaction runs away, possible causing an explosion, but more likely simply melting the metal and giving a lethal dose of radiation to anyone standing nearby.

Nuclear power stations avoid this by having control rods - graphite rods which are lowered into the reactor core to mop up spare neutrons and control the rate of reaction.

So you start off with things like uranium, and end up with lighter things like thorium



Another way to transform elements is nuclear fusion. Fusing two light elements together to produce a heavier one. This is the reaction going on in the sun and other stars, and also in hydrogen bombs and tokamak reactors (do a google search on tokamak).

The other way to transform elements is to bombard atoms of one element in a particle accelerator. This only works a few atoms at a time, so it's hardly a mass manufacturing process...

And that's it. There's really not many options. It can be done, but it's really, really hard. Much better, if you have a nanotechnological assembler, simply to have all the correct atoms to hand in the correct proportions in the first place...

H.

'Nuclear fission - the process used in all nuclear power stations, and the first nuclear weapons - is basically taking a heavy element (like uranium) and having it break down into two lighter elements.
When it does so, it gives off spare neutrons.'

Why is this?

And do you need to add neutrons to the two lighter elements on nuclear fusion?

Thirdly, are there any specially interesnting transition metals? We have to find out about one for homework and I'd like to do an interesting one if possible.

Yeah, thanks. Do you think this will be easier to do in the future? Does it happen often now or is it too cost effective?
jem

An atom consists of protons and electrons in equal number (to balance the electrical charges) and neutrons. In general the more protons in the nucleus, the more neutrons per proton are needed to stabilise the nucleus. Hence the two small atoms need fewer neutrons than the one large atom, and the surplus neutrons are ejected. Fission therefore turns large atoms into small ones. Fusion does the opposite.

See http://fusedweb.pppl.gov/CPEP/chart.html and pick "two key fusion processes" from the menu on the left for a better brief description than I could manage.

Noggin

"Thirdly, are there any specially interesnting transition metals?"

Top candidate, in my book, for interesting transition metals would have to go to Technetium, element 43. This is because all its isotopes are radioactive, and most of them have quite short half lives. This explains why there is no naturally occurring technetium anywhere on earth - the longest half life it has is 4 million years or so, and the earth is MUCH older than that (this is yet another stick you can beat creationists with - if the earth is only 6000 years old, why is every other element in the periodic table found naturally on earth, EXCEPT number 43?).

Menedeleev, when he first put together the periodic table, found gaps. He predicted the properties of technetium would be a bit like those of manganese, so he called it eka-manganese.

It was eventually discovered in 1937, if "discovered" is the right word. In fact, it was the first artificially produced element - if you slam deuterons (i.e. nuclei of heavy hydrogen, i.e. a proton and a neutron) into molybdenum (element number... FORTY TWO ) you get technetium. It has been manufactured in quite large quantities (i.e. kilograms) since.

It was one of the great triumphs of predictive science, because the element was very similar to what Mendeleev described, and the predictive power of his arrangement of elements was amply proven.

I'd say that's easily the most interesting transition metal. (Oh my god. How geeky and boring am I? I have a favourite transition metal for crying out loud!)

The only other transition metal which can hold a candle to technetium on the interesting register has to be mercury, simply for being a liquid at room temperature, which is just TOO weird.

H.

Thanks Hoo ! I was thinking of doing Technetium anyway, as a mater of fact, just because I liked the name.

It's interesting, but is it actually *useful* for anything (apart from waving at creationinsts in a truculent manner). I think I was meant to write about its uses as well

Tc-95 has a half life of only 61 days, and it gives off energetic gamma rays, so it's useful in tracing applications (dissolve a solution of a compound of the stuff in water, pump the water through a pipe, then walk along the pipe with a geiger counter. Hear a click? There's a leak. Better still, inject it into a human... seriously, they do that. The gamma rays are easily detectable, but if they're a small enough quantity they're not a risk.)

It's also a very good corrosion inhibitor if you mix it into carbon steel, but that's only really any good if the steel isn't near anything/anyone critical because... it's radioactive.

Below 11K it superconducts. Not a whole lotta use at that temperature, but hey...

H.

Oh, I forgot.

Technetium DOES occur naturally on earth, in one place - the Oklo reactor in Gabon. It's a (very rare) fission product of the nuclear reactor there.

H.

A fourth way--natural radioactivity. Some elements that have an unstable nucleus, including al isotopes of some of the heavier elements and some isotopes of lighter elements naturally decay into lighter elements by ejecting alpha (helium nuclei) and beta (electrons made by a neutron becoming a proton) particles from the nucleus.

"(this is yet another stick you can beat creationists with - if the earth is only 6000 years old, why is every other element in the periodic table found naturally on earth, EXCEPT number 43?)."

Might work, except for the same problem that every rational argument used against them has--they always blame it on God. For example "God created photons to look like they're coming from stars more than 6000 ly away"; "God created fossils to fool us", ect.

Still, a good point.

Call me RDO or Daneel or R. Daneel.

"God created photons to look like they're coming from stars more than 6000 ly away"; "God created fossils to fool us", ect.
I've never said that. Probably because i don't really know what photons are. (apologies if people have mentioned them before. i can't take in anything)
"(this is yet another stick you can beat creationists with - if the earth is only 6000 years old, why is every other element in the periodic table found naturally on earth, EXCEPT number 43?)."
So where is is naturally found? Mars? Venus? Zaarg? Sorry, that just came out. It doesn't say that there wasn't any before God livened up the world. The Bible doesn't say that God made the Earth, or does it. Doesn't it say 'the world was desolate and empty' or am i completely off the point. I'd better check.
Jem

'"God created photons to look like they're coming from stars more than 6000 ly away"; "God created fossils to fool us", ect.
I've never said that. Probably because i don't really know what photons are' Probably because you're not a creationist. Or are you? It hadn't occured to me, since you don't say anything to suggest it, but are you?

Photons are light particles, or light waves, depending on how you look at them. (It has to do with quantum mechanics. Basicly, they are sometimes waves and sometimes particles, and sometimes both.)

"So where is is naturally found? Mars? Venus? Zaarg?" Its found naturally in the remenants of recent supernovas. It is heavier than Iron-56, so it can't be produced except in supernovas, or from other elements by radiation, fission, or artificial augmentation.

"I've never said that." Perhaps, but some creationists, especially "young Earth" ones do. You might want to check out http://www.answersingenesis.com if you want to see what lunacy (I'm sorry if you're offended, but I don't see any other word for it that isn't as offensive) some creationists say.

I'm not offended.
clare, I don't know whether i'm a creationist or not. I don't know enough about the big bang or other theories to make a firm conclusion (as Hoo kindly informed me! )
Jem

Erm, hello everybody. Thought I might pop in here, hopefully not ruining the atmosphere, as I am reasonably confused about, well everything.

Hi Roadkill. Confused eh? Join the club.

Yes. The irony of it all is, the more you think you know, the less you actually do.

Bookmark.

F