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Fuison/fission, where does the energy come from?

  1. May 21, 2009 #1
    I've been wondering,
    Iron has the most binding energy per nucleon amongst elements and thus realized to be the most "stable" element.

    Smaller or bigger elements (compared to iron) can fuse or undergo fission respectively.
    As they fuse or undergo fission, it becomes more stable (the product element will have more binding energy per nucleon, losing its average mass per nucleon).

    This surplus in binding energy per nucleon comes from the rest mass deficit of the product atoms compared to the reactants.

    Atomic bombs use principles in fission and fusion. So, where does the energy released for the 'explosion' come from?

    if it comes from the mass deficit between product and reactant, where does the energy for the increase in binding energy come from?

    Thank you!
  2. jcsd
  3. May 21, 2009 #2
    Binding energy is negative. Otherwise elements would all just fall apart!
  4. May 21, 2009 #3


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    It comes from the force between nucleons.
  5. May 22, 2009 #4

    Andrew Mason

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    To add my two cents worth to the two correct responses above: The binding energy is the average energy required to unbind a nucleon from the nucleus. It doesn't come from anywhere because it is not a form of energy but an energy deficit. It is like gravitational potential energy. We say an object on the earth surface has -GmM/R of gravitational binding energy. It takes that much energy to unbind it from the earth's gravitation.

  6. May 22, 2009 #5
    it is known that to bring the two nuclei together(because there is electrostatic repulsion) , there is needed some force,supplied by external energy source,but when nuclei bring together they suffer opposing force cancelling net effect.But its important to notice than these external energy cannot be lost ,so this energy is added to binding energy(as nuclear energy),but the big amount of mass is lost contributing the energy release.Donot be confused that these beneficial energy came from loosing matter of nucleons and not from original binding energy.And talking about final binding energy its the original binding energy plus the kinetic energy (original external energy supplied)
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