Confusion regarding why conservation of mass number is not the same as conserving mass for nuclear reactions (1 Viewer)

[let aye = i]

If we conserve mass number we conserving the number of protons and neutrons and these r the things which contribute to the mass of an atom. So why is it that in a nuclear reaction while mass number is conserved mass is not

 

[Bob99]

If we conserve mass number we conserving the number of protons and neutrons and these r the things which contribute to the mass of an atom. So why is it that in a nuclear reaction while mass number is conserved mass is not

some mass is lost in the form of energy (E=mc^2)