Protons and neutrons are two kinds of particles (also called nuclei) that make up the nucleus. Their mass is almost equal, and their relative mass is 1, while the mass of electrons can be ignored compared with protons or neutrons, so the mass of atoms is mainly concentrated on the nucleus, that is, the relative atomic mass is equal to the number of protons plus the number of neutrons. The difference is that protons have a positive charge of one unit, while neutrons have no charge. So the number of charges carried by the nucleus, that is, the number of charges of the nucleus, is equal to the number of protons.