Question

why does hydrogen atom has less mass than the combined mass of proton and electron that makes it up? ​

Answer 1

Explanation:

The proton and electron of a hydrogen atom represent a bound system. By a bound system we mean that energy has to be supplied to liberate the two particles from each other, to make them free. ... Therefore, the mass of the bound system is necessarily smaller than the sum of the rest masses of the constituent particles

Answer 2

Explanation:

The proton and electron of a hydrogen atom represent a bound system. By a bound system we mean that energy has to be supplied to liberate the two particles from each other, to make them free. ... Therefore, the mass of the bound system is necessarily smaller than the sum of the rest masses of the constituent particles.