Empirical Formula
The simplest whole-number ratio of atoms of each element in a compound. It shows the ratio — not the actual number — of atoms present.
Example: Glucose has the molecular formula C₆H₁₂O₆. Its empirical formula is CH₂O because the ratio of C : H : O simplifies to 1 : 2 : 1.
Molecular Formula
The actual number of atoms of each element in one molecule of a compound. It is always a whole-number multiple of the empirical formula.
Example: Ethane has the empirical formula CH₃ and the molecular formula C₂H₆ — exactly two times the empirical formula.