If both the numbers of protons and neutrons are conserved in each nuclear reaction, in what way is mass converted into energy (or vice versa) in a nuclear reaction?

Explanation

In nuclear reactions, the numbers of proton and neutron is conserved and so is their rest mass on either side. However, the total binding energy on either side is not necessarily same and this difference in the binding energy of the reaction is released or absorbed in the form of energy. Since the total mass contributes to the binding energy, the difference in the total mass on either side is only responsible for the change in the energy. Thus nuclear reactions involve energy-mass interconversion.