Empirical formula: definition in chemistry
Empirical formula: The simplest whole-number ratio of the atoms of each element in a compound.
An empirical formula shows proportions, not the actual number of atoms in a molecule: glucose (C₆H₁₂O₆) and formaldehyde (CH₂O) share the empirical formula CH₂O. It can be found from experimental data by converting the mass or percentage of each element to moles and dividing by the smallest number. Formulas of ionic compounds such as NaCl and MgCl₂ are empirical formulas, because these compounds are lattices of ions rather than molecules.
Examples
- Glucose, C₆H₁₂O₆ — empirical formula CH₂O
- Hydrogen peroxide, H₂O₂ — empirical formula HO
- Benzene, C₆H₆ — empirical formula CH
- A compound of 40% sulfur and 60% oxygen by mass — SO₃
On the periodic table
Working out an empirical formula requires the atomic mass of each element from the periodic table to turn masses into moles.