Question

How is the formula for an ionic compound similar to the empirical formula for a molecular compound?

Answer 1

In molecular compounds, the empirical formula is obtained by simplifying the subscripts of the molecular formula, if possible, by dividinf them by a common factor. Thus, the empirical formula of glucose C_⁶H_¹²O₆ is CH₂O, wich indicates that for every atom of C, there are two atoms of H and one atom of O. The subscripts are always integers and if they are equal to 1 you dont have to write the number 1.
Meanwhile, in ionic compounds the empirical formula is the only one we can know, and indicates the ratio of the number of ions of each class in the ionic network. In magnesium hydride, there are two hybride ions per magnesium ion, then its empirical formula is MgH_2.