The chemical formula for cobalt(III) sulfate is Co2(SO4)3. The Co represents cobalt, the S represents sulfur, and the O represents oxygen. One atom of sulfur and four atoms of oxygen together represent sulfate.
The formula indicates that one molecule of cobalt(III) sulfate contains two atoms of cobalt, three atoms of sulfur and 12 atoms of oxygen. The chemical formula for a compound uses the chemical symbol to indicate which atoms are present and numbers in subscript to indicate the number of atoms of each element contained in the molecule. Formulas can be used for calculations, such as the percentage mass of each element in the molecule.