1. Identify the Ions:

* Iron(II): This indicates the iron ion has a +2 charge (Fe²⁺).

* Sulfate: This is the polyatomic ion SO₄²⁻.

2. Balance the Charges:

To form a neutral compound, you need one Fe²⁺ ion and one SO₄²⁻ ion. This gives you FeSO₄.

3. Include the Water of Hydration:

The "-7-hydrate" tells us that there are seven water molecules associated with each formula unit of the compound.

4. Write the Complete Formula:

The complete molecular formula is FeSO₄ · 7H₂O.