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Beta plus decay: mass balance?

  1. Aug 13, 2013 #1

    I am taking a radiochemistry class, and I am confused by beta plus decay.

    (1) p --> n + positron + electron-neutrino

    The mass of a proton is less than the mass of a neutron. In addition, the neutrino has mass as does the positron.

    (2) E = mc2

    There must be come sort of balance, must there not? Mass cannot be created unless energy is consumed. So where does the nuclei get the energy from to convert a single proton into three different particles, one of which has a larger mass than the proton itself?

    I hope I have made my confusion understandable. Also, my macbook would not let me use the greek characters or sub- and superscript.

  2. jcsd
  3. Aug 13, 2013 #2


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    The beta-plus decay cannot occur in a single proton due to the need for energy to be supplied from some external source.

    See: http://en.wikipedia.org/wiki/Beta_decay

    In heavier nuclei, beta-plus decay can occur if the original nucleus has a higher binding energy than the nucleus which remains after the emission of the beta-plus particle.
  4. Aug 13, 2013 #3
    Ahh, that makes sense. Thank you for your help.
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