What does an empirical formula show?

• A. Simplest ratio
• B. The exact number of atoms
• C. The bonds
• D. The mass numbers

Answer: (A)

The empirical formula shows the simplest whole-number ratio of atoms in a compound. It comes from experimental composition data and is found by converting masses to moles and simplifying the ratio to the smallest whole numbers. This tells you which elements are present and in what proportions, but it doesn’t give the exact number of atoms in a molecule or how those atoms are bonded. The actual molecule could have exactly the same ratio (empirical equals molecular) or could be a multiple of that ratio, so the molecular formula might be larger. It also doesn’t convey information about bonds or the mass numbers of the atoms.