The atomic number of the periodic table directly corresponds to the number of protons which is in the atom. Once another proton is added, it is no longer the same element. The same cannot be applied to when another neutron or another electron is added. Adding more electrons will give the atom a negative charge and removing electrons will give the atom a positive charge. Metals tend to lose electrons, which creates a positive charge. Non-metals tend to gain electrons, forming a negative charge. Electrons are the foundation for determining how compounds are formed among atoms.