When Metals Have More Than One Cation

• Some transition metals can have more than one cation. For example, copper can have a +1 or a +2 charge.

• We can tell the charge of the metal because it is written in as a roman numeral in the name. This is called the stock system for naming.

E.g. write the formula for copper (I) sulfide Cu 1+ S 2 Cu 2 S

E.g. write the formula for copper (II) sulfide Cu 2+ S 2 Cu S

Naming and the Stock System • We can find the name of a compound using the stock system.

• We use a reverse criss-cross method

Naming and the Stock System FeCl 3 Iron can have a +2 or a +3 charge.

Fe ? Cl 1 There are 3 negative charges, therefore Fe must be +3.

We would call it Iron (III) chloride.

Naming and the Stock System Cu 2 S Copper can have a +1 or a +2 charge.

2 Cu ? S 2 Two atoms of Copper (I) will make a 2+ charge (1+ x 2 atoms of Cu= 2+).

We would call it Copper (I) sulfide.