1.The symbol of an atom changes when the number of changes.
2.The net charge of an atom depends on and
.
3.The atom is neutral when and are equal.
4.The mass number of an atom depends on and
.

Because electrons have negligible mass, to account for the mass of the isotope, there must be 16 neutrons, 16 neutrally charged, massive, fundamental particles present in the sulfur nucleus. and thus finally, if we have the 32s2− ion, there are 18 electrons, 16 protons, and 16 neutrons.