Empirical formulas (Simplest Formulas)
An empirical formula (also known as a simplest formula) is the simplest whole number ratio of the atoms in a compound.
For example: The formula C4H10 is not an empirical formula, because both the 4 and the 10 can be divided by 2. The simplest formula for that compound would be C2H5. The formula C3H8, on the other hand, is an empirical formula because neither the 3 nor the 8 have a common factor (other than 1).