An ion formula is what is called an empirical formula, which simply represents the ratios of atoms in the compound. In sodium chloride, NaCl, for ever atom of sodium, there is an atom of chlorine. Covalent bonds form between atoms that do not have a significant difference in electronegativity.Almost all covalent are formed between non-metals and atoms of the same kind (such as chlorine-chlorine molecules). There are two important types of covalent bonds: non-polar and polar bonds.olecular (covalent) compounds are between only non-metals. (Metallic compounds are between metals and other metals) An io … nic compound is a pure substance that is formed from a metal and a nonmetal. It has a fairly high melting point and is a conductor of electricity when in a molten or aqueous state.