Question

If both the number of protons and the number of neutrons are conserved in a nuclear reaction like

in what way is mass converted into energy? Explain.

Answer 1

In fact the number of protons and number of neutrons are same before and after a nuclear reaction, but the binding energies of nuclei present before and after a nuclear reaction are different. This difference is called the mass defect. This mass defect appears as energy of reaction. In this sense a nuclear reaction is an example of mass-energy interconversion.