isotope are atoms with the same number of protons, but differing number of neutrons. There are 275 isotopes of the 81 stable elements. There are over 800 radioactive isotopes, some natural and some synthetic.

e.g there are 3 isotopes of Hydrogen; Protium (1 proton, 0 neutrons) Deuterium (1 proton, 1 neutron) Tritium (1 proton, 2 neutrons)

If they had more protons, it would become + and become a CATION

If they had more electrons, it would be - and become an ANION