Copper (II) is a cation with a +2 charge. Sulfide is an anion, with a -2 charge.
Work Step by Step
There is no overall charge on the compound, Thus the charges are balanced. Sulfide has a -2 charge, therefore in order to balance charges, copper has a +2 charge making it 'Copper (II)'. Also, Sulfur can gain 2 electrons, making it a sulfide anion and thus, copper can loose 2 electrons from its outer most shell making it a copper (II) cation.