Man-made chems

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Offline Nobody's Confidant

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Man-made chems
« on: 26/10/2007 17:22:45 »
Why are synthetic elements the heaviest, and why do they deteriorate so fast?
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Offline DoctorBeaver

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Man-made chems
« Reply #1 on: 26/10/2007 17:43:40 »
In simplistic terms, the weight of an atom depends on the number of protons & neutrons in the nucleus as electrons are too light to make any real difference (not strictly accurate, but it'll do).

Hydrogen is the lightest element and has 1 proton. Obviously, you can't have less than 1 proton or there would be no nucleus to the atom. All stable arrangements between the lightest & heaviest elements are already used. Therefore, any synthetic elements must be heavier than the heaviest naturally occuring element, which is Uranium (92 protons, 146 neutrons).

As for why they are unstable, an unstable atom does not have enough binding energy to hold the nucleus together. I think the positive charges of the protons provides enough repulsion to force the nucleus apart.

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Man-made chems
« Reply #2 on: 26/10/2007 19:26:58 »
There are many synthetic isotopes that are fairly light, but they are merely isotopes of elements where other, stable, and naturally occurring, isotopes are already known.

Synthetic isotopes (insofar as they are synthesising something that is other than a synthetic copy of what already naturally occurs) must have a short half-life, otherwise it would also occur naturally.

A case in point is plutonium - the first of the transuranic elements, and so the first element that is regarded as artificial.  When the solar system was young, some plutonium would have existed, but over time, that plutonium would have decayed, so there is none left for us to discover, so all that we have is that which we create ourselves (there is a caveat to this, in that very very small amounts of plutonium still do get produced in Uranium mines, but given that Uranium is a filise material, if more than a small amount was ever produced, it would explode, and you would have none left - and there is some evidence this may have happened in the early history of the Earth).