how RaCI is radium chloride but SeCI2 is selenium dichloride not necessary when there is one possible way of naming compounds such as Ex MgCI2 magnesium chloride Roman numeral is representing a charge of cation and text shows how many element is present 22 a RaCI2 radium chloride b SeCI2 selenium chloride c PCl3 Phosphonus chloride d Na3P sodium phosphate e MnF2 Maganese II Fluoride F ZnO Zinc Oxide 41 a cobalt II chloride CoCl2 c Sodium phosphide Na3P d iron II oxide FeO e Calcium hydride CaH2 f Manganese IV oxide MnO2 g Magnesium iodide MgI2 h copper I sulfide Cu2S 43 a Carbon disulfide CS2 b water H2O c Dinitrogen trioxide N2O3 d Dichloride heptoxide Cl2O7 e Carbon dioxide CO2 f ammonia NH3 g Xenon tetrafluoride XeF4 44 a Diphosphorus monoxide P2O b Sulfur dioxide SO2 c Diphosphorus pentoxide P2O5 d Carbon tetrachloride CCI4 e Nitrogen tribromide NBr3 f Silicon tetrafluoride SiF4 g Sulfur dichloride SCI2