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Finding the binding energy for lithium

  1. Apr 14, 2009 #1
    1. The problem statement, all variables and given/known data
    Find the binding energy (in MeV) for lithium 3Li8 (atomic mass = 8.022486 u).

    2. Relevant equations
    Binding energy = (#p)(mass proton) + (#n)(mass neutron) - (mass nuclei*c^2)

    3. The attempt at a solution
    mass proton = 1.007825
    mass neutron = 1.008665
    Binding energy = (3)(1.007825) + (5)(1.008665) - (8.022486*(3e8)^2)
    Binding energy = -7.22e17 J x 1 eV/1.602e-19 J = -4.506e36 eV x 1e-6 MeV / 1 eV = -4.506e30 MeV
  2. jcsd
  3. Apr 14, 2009 #2


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    Staff Emeritus
    Science Advisor
    Gold Member

    Check your units please. Also your formula for binding energy is wrong. Check the c2's.
  4. Apr 14, 2009 #3
    Oops, sorry I know I typed the formula wrong on here, but I did it the correct way on my homework... It's still telling me my answer is incorrect. :/
  5. Apr 14, 2009 #4


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    Staff: Mentor

    mass proton = 1.007825
    mass neutron = 1.008665

    are atomic mass units (amu). Be careful about mixing units.

    If one is using c = 3 x 108 m/s, then one must use atomic masses in kgs.
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