# What is the total number of protons and neutrons in the nucleus of an atom?

Protons and neutrons are massive particles. The combined number of $\text{protons}$ and $\text{neutrons}$, of $\text{nucleons}$, constitute the mass of the atom. The $\text{electrons}$, while they do all the chemistry, are along for the ride, and do not make much contribution to the atomic mass. Certainly from a chemical perspective, their mass is negligible. From a physical perspective you will have to ask on the other forum.