A brand new Battery has a mass of 249.6g. After it's been fully discharged, it's mass is still 249.6g. Explain.
An electron has no known components or substructure. It is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton and it is 9.10938291(40)×10^−31 kg. As can you see it is very and very small number in comparison to grams, that are 2.496×10^-1. It means that you can not show mass of lost electrons in grams. That's why the mass of battery is the same (in grams) before and after discharging.