Step #4 - since a formula must have zero total charge, you write the formula Cu 2 O. Example #3 - Write the formula for: iron(III) sulfide. Step #1 - the symbol of the cation is Fe. Step #2 - the charge on the cation is a positive three. remember, that comes from the Roman numeral. Step #3 - Sulfide (the anion) means S 2 ¯.
The first four moments of a distribution about the value
N2O4 dinitrogen tetroxide PCl5 phophorus pentachloride SO2 sulfur dioxide SO3 sulfur trioxide CS2 carbon disulfide Br2O7 dibromine heptoxide CO carbon monoxide P2O3 diphosphorus trioxide Cl2O dichlorine monoxide SF6 sulfur hexafluoride Exercise: Give formulas for the following: iodine pentabromide IBr5 chlorine dibromide ClBr2 oxygen difluoride OF2