In the process of charging a body either gains or loses electrons to get negatively or positively charged. This transfer of electrons doesn’t bring any observable change in the mass of the body. Reason being, the mass of electron is very small compared to the charged body. However, we can still calculate the change in mass of a body due to the charging process.
Example:
Suppose a body of mass ‘M’ is given charge +q.
Since, charge is quantized, therefore, q = ne.
So, mass of electrons lost is = n × me [me is the mass of an electron]
Thus, the new mass of the body is = M – n × me
