Which statement describes the empirical formula?

• A. The actual number of atoms of each element in a compound
• B. The simplest whole-number ratio of atoms in a compound
• C. The total charge of the compound
• D. The mass of the compound

Answer: (B)

Empirical formula is the simplest whole-number ratio of atoms in a compound. It shows how many atoms of each element are present relative to each other, not the exact number of atoms in every molecule. You get it from experimental data, like percent composition, by converting masses to moles and reducing the ratios to the smallest integers. For example, if the mole ratios come out as 2:1 for two elements, the empirical formula will reflect that ratio (and not the full molecular formula, which could be a multiple of the empirical one). The other statements describe either the actual number of atoms in a molecule (molecular formula), the overall charge, or the mass, which are not what the empirical formula represents.