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Why nuclear radiations occur in atoms with large nucleus?

  1. Jun 27, 2013 #1
    why nuclear radiations occur in atoms with large nucleus?Is it the weakening of residual strong force?
    If so why it gets weak ?
     
  2. jcsd
  3. Jun 28, 2013 #2

    SteamKing

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    Radiation also occurs in atoms with a small nucleus, for example tritium (H-3) and carbon-14.
     
  4. Jun 28, 2013 #3

    mfb

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    It does not get weak, but the repulsion between all those protons grows quicker than the binding due to the residual strong force*. Therefore, as a general tendency, very big nuclei are more likely to decay in some way.

    *the binding energy due to the strong force is (approximately) proportional to the number of nucleons. On the other hand, every proton is repelling every other proton in the nucleus - this contribution grows with the squared proton number.

    Small nuclei with a very unbalanced proton/neutron ratio are unstable, too.
     
  5. Jul 20, 2013 #4
    But in tritium atom there is only one proton.Hence there will be no repulsion.So why do it radiate??
     
  6. Jul 21, 2013 #5
    Imbalance between protons and neutrons. A lone neutron radiates as well.

    In fact, tritium atom radiates much less energy than a lone neutron does. A deuteron repels a proton, and that decreases the radiation energy of the extra neutron. Just not enough to stop the radiation altogether, like with lithium 7.
     
  7. Jul 21, 2013 #6

    mfb

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    The part you quoted was about alpha radiation - something you mainly find at big nuclei.

    Helium-3+electron+neutrino is lighter than tritium (the mass difference between protons and neutrons is relevant here), therefore tritium can decay.
     
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