Identify the correct formula for nickel(II) sulfate.

The formula for nickel(II) sulfate is NiSO4. In chemical nomenclature, the Roman numeral in the name indicates the oxidation state of the metal. Nickel(II) means that nickel has a +2 charge.

Sulfate is a polyatomic ion represented by SO4, which carries a -2 charge. To form a neutral compound, the +2 charge from one nickel ion (Ni²⁺) balances the -2 charge from one sulfate ion (SO4²⁻). Therefore, the correct formula simply combines one nickel ion with one sulfate ion, resulting in NiSO4.

This straightforward combination reflects the stoichiometry of the ions involved and confirms that for each nickel(II) ion, one sulfate ion is required, leading to this particular formula.