Final answer:
Empirical formulas show the simplest whole-number ratio of elements in a compound, with ionic compounds having a formula that matches the actual arrangement of ions. In contrast, molecular compounds' molecular formulas may be an integer multiple of the empirical formula, indicating the real number of atoms within the molecule.
Step-by-step explanation:
Understanding Empirical Formulas
Empirical formulas represent the simplest whole-number ratio of elements in a compound, without showing the actual number of atoms. For ionic compounds, which consist of a repeating pattern of ions, the empirical formula is the same as the actual formula, such as NaCl for sodium chloride. In contrast, molecular compounds may have molecular formulas that contain a multiple of the empirical formula. For example, ethene has a molecular formula of C2H4, but its empirical formula is CH2, indicating a simple 1:2 ratio of carbon to hydrogen atoms.
The formula mass of ionic compounds, as with Na2S, corresponds to the sum of the atomic masses of the elements in their empirical formula. This reflects the ratio of ions comprising the compound in its solid state. For molecular compounds, molecular formulas are determined by the comparison of the compound's molar mass to its empirical formula mass. The molecular formula is always an integer multiple of the empirical formula, which expresses the actual count and distribution of atoms within a molecule.