The nuclear mass M is always less than the total mass, Sm, of its
constituents The difference in mass of a nucleus and its constituents
is called the mass defect,
DM = (Z mp + (A – Z )mn) – M
Using Einstein’s mass energy relation, we express this mass difference
in terms of energy as
DEb = DM c2
The energy DEb represents the binding energy of the nucleus In the
mass number range A = 30 to 170, the binding energy per nucleon is
nearly constant, about 8 MeV/nucleon 8