Calculate the empirical formula of a compound containing 77.7% Iron and 22.3% of oxygen.

An empirical formula is the simplest whole number ratio of atoms of each element present in the compound.1) Divide by atomic relative mass to find the number of moles. 2) Find a ratio between the moles. 3) Divide the ratios by smallest number. 4) Obtain the number of atoms.1:1 ratio, therefore FeO.