empirical formula
An empirical formula is a formula that shows the elements in a compound in their lowest whole-number ratio. Glucose is an important simple sugar that cells use as their primary source of energy. Its molecular formula is C 6 H 12 O 6 . Since each of the subscripts is divisible by 6, the empirical formula for glucose is CH 2 O. When chemists analyze an unknown compound, often the first step is to determine its empirical formula. There are a great many compounds whose molecular and empirical formulas are the same. If the molecular formula cannot be simplified into a smaller whole-number ratio, as in the case of H 2 O or P 2 O 5 , then the empirical formula is also the molecular formula.