Electrons have less mass than either protons or neutrons. In a neutral atom there are always equal numbers of protons and electrons. Isotopes are a family of atoms all of which have the same number of electrons. Electrons are found in clouds called orbitals surrounding the atomic centers. Electrons are sometimes exchanged between atoms.
Ions are atoms that have gained or lost electrons.
Ions always have a positive charge. Atoms are at their most stable when their outermost electron energy level is completely filled or completely empty of electrons. Hydrogen atoms and Helium atoms both have two protons in their atomic centers, but different numbers of neutrons. The atomic mass of all isotopes within a family of atoms is always the same. The atomic number of all isotopes within a family of atoms is always the same.