A representation that shows the total number of atoms or elements present in a substance along with their relative proportions is called the chemical formula of the substance.
For example, the chemical formula of hydrogen chloride is , where both hydrogen and chlorine are present in 1:1 ratio.
Formula of Gold (III) sulfide:
Gold (III) sulfide contains atoms of gold with three positive charges and sulfur having two negative charges. Therefore, in order to balance out the charges two atoms of gold and three atoms of sulphur are required.