For our purposes we will concentrate only on three of them. The neutron has no charge, and a mass of slightly over 1 amu. Some scientists propose the neutron is made up of a proton and electron-like particle. The electron is a very small particle located outside the nucleus. Because they move at speeds near the speed of light the precise location of electrons is hard to pin down.
Electrons occupy orbitals, or areas where they have a high statistical probability of occurring.
The charge on an electron is -1. The atomic number is the number of protons an atom has. It is characteristic and unique for each element. Isotopes can be used to determine the diet of ancient peoples by determining proportions of isotopes in mummified or fossilized human tissues. Biochemical pathways can be deciphered by using isotopic tracers.