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Author Topic: Periodic table  (Read 7066 times)

paul.fr

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Periodic table
« on: 09/03/2007 00:55:46 »
Have we found all of the elements, or do you think there are new ones out there?


 

another_someone

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« Reply #1 on: 09/03/2007 06:38:46 »
What do you mean by 'finding new elements'?

All the naturally occurring elements (those up to uranium or plutonium) that theoretically can can exist have now been isolated.  Transuranic elements do not naturally occur on this planet (although it is possible they may be created in some supernova, or other cosmic processes).  We have created a fair number of transuranic elements, and no doubt as time progresses, we will constantly be creating new, heavier, elements, most of which which rapidly decay into something less exotic in the blink of an eye (together with a flash of radiation, that you probably don't want to get too close to your eye anyway).
 

Offline lightarrow

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« Reply #2 on: 09/03/2007 12:30:37 »
How would a 10 cm big Super-heavy esotic atom look like?  [:0]
 :)
 

Offline daveshorts

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« Reply #3 on: 09/03/2007 13:16:03 »
Like an immense exploding nuclear bomb, as it wouldn't even begin to be stable, and at normal pressures the neutrons would decay to protons very rapidly, and the repulsion from those would be enough to rip it apart immensely violently.

Remember the energy from an atomic bomb is released from a nuclei with only 240 odd neutrons and protons... you are talking at the very least 1025 assuming it had the same density as normal matter..
 

another_someone

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« Reply #4 on: 09/03/2007 17:14:29 »
Firstly, while there would be great repulsive forces with such an atom, it would be a pretty massive atom, with a significant gravitational pull (at least close to the nucleus, given the density of the nucleus).

Secondly, electron orbits that large would have peculiar effects of their own - would the nucleus be able to hold on to its electrons - and there would be a massive charge spaced out over that 10 cm (assuming we are talking about a complete atom, not merely a denuded nucleus - although the nucleus itself would have a massive charge, but you would not even have the electrons on the outside to balance the charge at a distance).

I believe the neutron decay alone has a half life of about 13 seconds, so that gives a good few seconds where this massive gravitational and electrostatic ball is interacting with the environment around it.  One interesting issue is that during all of that time, I would imagine it would have enough force to tear molecules (and maybe atoms) around it apart - thus it must be losing energy to its environment by that means.  Where would that energy be coming from?
 

Offline daveshorts

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« Reply #5 on: 09/03/2007 17:22:57 »
I think it would need a tiny proportion of the neutrons to decay for it to explode, electrostatic forces are enormously strong.
 

another_someone

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« Reply #6 on: 09/03/2007 22:22:05 »
I think it would need a tiny proportion of the neutrons to decay for it to explode, electrostatic forces are enormously strong.

The more I look at this, the less sense I make of it.

Clearly, there would be serious hurdles to overcome to get that number of nucleons into a single nucleus in the first place, but if you can overcome those hurdles, I cannot see that a few percent more of less will make any qualitative difference.

The electrostatic charge of the protons in the atom is balanced by the charge of the electrons, but the electrons would have little influence on what happens within the nucleus itself, and play no part in the stability of the nucleus, therefore a nucleus is always electrostaticaly unbalanced, so adding a few more protons will not shift it from a balanced postion to an unbalanced position.
 

Offline daveshorts

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« Reply #7 on: 10/03/2007 23:00:22 »
The only way you could possibly make a nucleus that big, would be to make it 99.99% neutrons, this is because the electrostatic repulsion forces are very large and as a nucleus gets larger they overcome the strong nuclear force which is very short range (doesn't have a lot of effect more than one neucleon away), so the only way to stop it ripping itself apart would be to make it mostly neutrons.

However neutrons on their own decay is 13seconds as you say and it would only take a minute proportion of all these neutrons to decay by spitting an electron out of the nucleus, and turning into a proton to cause the repulsion to overcome the strong nuclear force, and the whole thing to explode.
 

another_someone

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« Reply #8 on: 11/03/2007 00:30:55 »
How easily would an electron manage to leave such a large nucleus?

For a small nucleus, or for a neutron on the edge of such a large nucleus, one could imagine the electron would leave fairly easily; but for a neutron near the core of such a large nucleus, would there not be a strong possibility that any electron it emits would be captured by another proton within the nucleus, and so reestablishing the balance between neutrons and protons.

It is ofcourse far more possible for a neutron on the periphery of such a nucleus to be able to eject an electron out of the nucleus, but would that actually cause the entire nucleus to shatter, or merely cause a few nucleons on the periphery to evaporate off (and who cares about a few nucleons when to have 10[super]25[/super] of them.

The other question is, will some of the protons also have a possibility of converting to neutrons by emission of a positron?  Under what circumstances does positron emission happen, and how would that effect the overall nucleus?
 

Offline lightarrow

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« Reply #9 on: 11/03/2007 10:41:36 »
I have no idea of how much a neutron would be stable inside a given nucleus, and especially inside such a big nucleus. Outside a nucleus a neutron is less stable, half life ≈ 10 minutes, as you said. About protons, they have a very long life: ≈ 1035 years.
However an interesting feature of an atom like that would be that, probably, outer electrons would orbit classically around the nucleus.
 

Offline Bored chemist

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« Reply #10 on: 11/03/2007 13:30:45 »
This reminds me of a thought I once had.
Imagine that you have a neutron star with some utterly huge number of neutrons. Add a single proton. Do you now have the nucleus of some absurdly heavy isotope of hydrogen?
 

Offline lightarrow

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« Reply #11 on: 11/03/2007 19:03:00 »
This reminds me of a thought I once had.
Imagine that you have a neutron star with some utterly huge number of neutrons. Add a single proton. Do you now have the nucleus of some absurdly heavy isotope of hydrogen?
Wow! Very interesting! And how would be water made of that isotope of hydrogen?  ;)
 

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« Reply #11 on: 11/03/2007 19:03:00 »

 

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