The chemical formula of iron(II) sulfide is FeS.
Iron(II) refers to iron in its +2 oxidation state. In this compound, iron (Fe) has lost two electrons, resulting in a charge of +2. Sulfide (S) ions carry a charge of -2. When these two ions combine, they form a neutral compound.
The formula can be understood by recognizing that one iron(II) ion (Fe²⁺) balances one sulfide ion (S²⁻), leading to the overall charge of the compound being zero. Hence, the simplest ratio of iron to sulfur in iron(II) sulfide is 1:1, resulting in the formula FeS.