Metals naming multiple-cation metal compounds

Naming Compounds Involving Multiple-Cation Metals... 

Use the Stock method to name these ionic compounds involving multiple-cation metals. 

A compound containing a metal that forms multiple cations must have a Roman numeral in its name. 

Ionic compounds that contain polyatomic ions are named in the same way used to name binary ionic compounds. Attention must be paid as to whether the cation is a metal that forms a single cation or multiple cations, and the name of the polyatomic ion is that given in the table. Note how these six ionic compounds are named ... 

Fe2(S04)3 This compound contains a multiple-cation transition metal, and the charge on the cation must be determined to write a correct name. There are three sulfate ions in parentheses, giving a total negative charge of 6- (3x2- = 6-). The two iron ions then must be iron(III) ions, Fe3+ (2x3+ = 6+), to balance the negative charge of the sulfate ions. The systematic name of the compound is iron(III) sulfate. 

Group lA and group 2A metals have only one oxidation number. Transition metals and metals on the right side of the periodic table often have more than one oxidation number. To distinguish between multiple oxidation numbers of the same element, the name of the chemical formula must indicate the oxidation number of the cation. The oxidation number is written as a Roman numeral in parentheses after the name of the cation. For example, the compound formed from Fe + and has the formula FeO and is named iron(II) oxide. The compound formed from Fe + and has the formula Fe203 and is named iron(III) oxide. 

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