A molecular formula is one in which all of the atoms in the compound are listed. For example, if I have the molecular formula ##C_2H_6##, I know that there are two carbon atoms and six hydrogen atoms in the molecule.
However, in the case of , there are no molecules to make a molecular formula. As a result, we’re left with the ratio of the to one another, which is the empirical formula. Since the ratio of magnesium to oxygen is 1:1, the formula is MgO.
OK.
