Ferrous sulfate is a chemical compound with the formula FeSO₄. It is typically found as a hydrate, meaning it has water molecules attached to its structure. The most common form is ferrous sulfate heptahydrate (FeSO₄·7H₂O), which has the following ingredients:

* Iron (Fe): The central metal ion.

* Sulfur (S): Part of the sulfate anion.

* Oxygen (O): Part of the sulfate anion and the water molecules.

* Hydrogen (H): Part of the water molecules.

Therefore, the ingredients of ferrous sulfate are iron, sulfur, oxygen, and hydrogen.