The molecular formula of iron oxide can vary depending on the oxidation state of iron and the stoichiometry of the compound. The two most common forms of iron oxide are ferrous oxide (FeO) and ferric oxide (Fe2O3).
Ferrous oxide (FeO): In this compound, iron has an oxidation state of +2.
Ferric oxide (Fe2O3): In this compound, iron has an oxidation state of +3.
Sodium chloride, on the other hand, has a simple and well-known molecular formula, which is NaCl. Sodium chloride is an ionic compound composed of sodium ions (Na+) and chloride ions (Cl-).