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Author Topic: Why are some substances radioactive, but not others?  (Read 9478 times)

Offline Muhammad Iqbal Khan

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Q1: why do some atoms radiate and other don't? what is the cause for radiation ?
« Last Edit: 08/04/2008 09:07:39 by chris »


 

Offline lightarrow

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Re: Why are some substances radioactive, but not others?
« Reply #1 on: 27/02/2008 15:02:21 »
Q1: why do some atoms radiate and other don't? what is the cause for radiation ?

The reason is in their nuclei's stability. Remember that the coulombian force tend to make protons repel from each other, while the strong force makes nucleons (protons and neutrons) attract to each other.

The problem is that the first force has an infinite range, while the latter has a finite range; to make a metaphore, you can figure protons and nucleons as little ping-pong balls, some of them positively charged, and wich all have a sticky surface; when you put  them together, you can find that your "clump" of balls is stable only if you didn't put in many charged balls, in percent but also as total amount; when the clump is almost stable but not exactly, the coulombian force will make it break or expel some charged ball and in doing this, reaching stability. This process is the analogue of radioactivity.

Actually the process is much more complicated because there are also other kinds of forces and, for example, the nucleus can also expel neutrons or smaller nuclei, or electrons, or just radiation, to reach greater stability.
« Last Edit: 27/02/2008 15:08:17 by lightarrow »
 

lyner

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Why are some substances radioactive, but not others?
« Reply #2 on: 10/04/2008 17:09:02 »
But then, why don't neutrons stick together in clumps? There is no electric force to push them apart.
There just isn't a simple explanation. Atomic structure is hard enough but nuclei are devils!
 

Offline Supercryptid

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Why are some substances radioactive, but not others?
« Reply #3 on: 11/04/2008 01:42:36 »
I'm not exactly sure about my following explanation: from what I know, you can stick 2 neutrons together with the strong nuclear force. However, I believe the resulting "dineutron" would be more stable if it could decay into a deuteron. For that reason, it does decay by emitting an electron and an electron antineutrino. I think something similar would happen if you stuck larger clumps of neutrons together as well.
 

lyner

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Why are some substances radioactive, but not others?
« Reply #4 on: 12/04/2008 21:08:03 »
Fair enough!
Thanks.
 

Offline Soul Surfer

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Why are some substances radioactive, but not others?
« Reply #5 on: 14/04/2008 17:27:38 »
You have to remember that a neutron on its own decays into a proton with a half life of about 12 minutes.  dineutrons are I think even less stable
 

Offline syhprum

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Why are some substances radioactive, but not others?
« Reply #6 on: 14/04/2008 19:08:34 »
Large clumps of Neutrons 10^30/31 Kg are possible where they are held together by gravity I am not sure but I don't think there is any spontaneous decay.
 

Offline daveshorts

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Why are some substances radioactive, but not others?
« Reply #7 on: 15/04/2008 16:08:26 »
Yes neutron stars have so much gravity that the gravitational energy you release by turning a proton and an electron into a neutron  and taking up less space is greater than the nuclear energy that you loose by doing this, so although there are probably some protons and electrons in a neutron star they will combine back to form neutrons quite quickly.
 

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Why are some substances radioactive, but not others?
« Reply #7 on: 15/04/2008 16:08:26 »

 

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