How Do You Calculate Mass Defect and Binding Energy in Nuclear Physics?

[Oli9116]

Hi i just wanted to clarify a few things to do with nuclear physics so if anyone could help me that would be great.

1. When calculating the mass defect do you use the given mass (the one the periodic table or the data sheet) - the mass of the protons, neutrons AND electrons or do you just forget about the mass of the electrons?

2.When calculating the binding energy using E=mc2 is the m the mass defect?

If anyone could help clarify these that would be great and if I'm totally of track if you can explain the concept to me I would really appreciate it.

Thanks

 

[Astronuc]

Hi i just wanted to clarify a few things to do with nuclear physics so if anyone could help me that would be great.

1. When calculating the mass defect do you use the given mass (the one the periodic table or the data sheet) - the mass of the protons, neutrons AND electrons or do you just forget about the mass of the electrons?

2.When calculating the binding energy using E=mc2 is the m the mass defect?

If anyone could help clarify these that would be great and if I'm totally of track if you can explain the concept to me I would really appreciate it.

Thanks

When calculating the nuclear mass defect, ideally one should use the nuclear masses rather than atomic masses. However, atomic masses can be used since the masses of the electrons should cancel. This approach is reasonably accurate for light nuclei where the electron binding energies are on the order of eV. However, for heavy elements where the K,L binding energies are on the order of keV, the error for fission calculations could be on the order of keV.

Using E = mc², the m is actually a Δm which is the difference in mass (products) - mass (reactants). For example, if one does an alpha decay, 92U238 => 90Th234 + 2He4

http://hyperphysics.phy-astr.gsu.edu/hbase/nucene/nucbin.html#c1
http://hyperphysics.phy-astr.gsu.edu/hbase/nuclear/radser.html#c3