Rules for Naming Monatomic Ions Positive ions--Cations 2.If a metal can form different cations,the positive charge is indicated by a Roman numeral in parentheses following the name of the metal Fe:iron(II)ion Cu:Copper(1)ion Fe iron(III)ion Cu2+Copper(II)ion An older method: -ous the lower charged Fe2*:ferrous ion Cu'cuprous ion -ic the higher Fe:ferric ion Cu:cupric ion charged2. If a metal can form dif erent cations, the positive charge is indicated by a Roman numeral in parentheses following the name of the metal 2 3 : ( ) : ( ) Fe iron II ion Fe iron III ion   + 2 : C ( ) : ( ) Cu opper I ion Cu Copper II ion  -ous : the lower charged -ic : the higher charged An older method : 2 3 : Fe : ferr ion Fe fer ous ric ion   2 : : Cu cupr ion Cu cup ous ric ion  