Answer: the sum of the masses of the individual protons and neutrons is less than the mass of the stable Nucleus
Explanation:
Nuclei fission involved bonds breaking with the loss of quantity of Energy by the protons and Neutrons
Remember : e=mc2
Therefore, this breakage of bonds result in loss in masses of p and n.
However, in intact Nucleus the energies of the p and n are trapped in the intact bonds holding them together therefore heavier masses than when broken down.