(b) We know that the binding energy of a nucleus gives a negative
contribution to the mass of the nucleus (mass defect) Now, since
proton number and neutron number are conserved in a nuclear
reaction, the total rest mass of neutrons and protons is the same
on either side of a reaction But the total binding energy of nuclei
on the left side need not be the same as that on the right hand
side The difference in these binding energies appears as energy
released or absorbed in a nuclear reaction