In nuclear fission and fusion the mass defect is

In nuclear fission and fusion the mass defect is

The nuclear binding energy is actually nothing but the energy that is used to breakdown a nucleus into its constituent units, the protons and the neutrons. The whole nucleus weighs a lot lesser than the combined mass of the individual protons and neutrons. When the neutrons and the protons forms a nucleus(nuclear fusion) or when a nucleus is split to give out the individual components(nuclear fission), a specific amount of energy is expelledThis energy is represented by the mass that is missing, the difference between the mass of the nucleus as a whole unit and the combined mass of the constituent units; This is called the mass defect.

60.0 - there are 3 significant numbers