If we separate a nucleus into its nucleons, we would have to supply a
total energy equal to Eb, to those particles Although we cannot tear
apart a nucleus in this way, the nuclear binding energy is still a convenient
measure of how well a nucleus is held together A more useful measure
of the binding between the constituents of the nucleus is the binding
energy per nucleon, Ebn, which is the ratio of the binding energy Eb of a
nucleus to the number of the nucleons, A, in that nucleus:
Ebn   =  Eb / A
(13 9)
We can think of binding energy per nucleon as the average energy
per nucleon needed to separate a nucleus into its individual nucleons