This is caused by having a different number of neutrons in the nucleus. For example matter and mass can be interchanged. It is not shown on the periodic chart. The electron's mass is 10-31kg. It separates isotopes according to charge and mass.
Solids melt and liquids evaporate when the van der waals forces between molecules are broken.
It contains two or more atoms. The protons are deep down in the nucleus and stay there. So electrons are either added or subtracted to make ions. Free elements have zero as an oxidation number. Only two electrons may occupy an orbital, but they must have opposite spins.