The formula for iron(II) sulfite is FeSO₃. Here's how to figure that out:

* Iron(II) means the iron ion has a +2 charge (Fe²⁺).

* Sulfite is the polyatomic ion SO₃²⁻.

To balance the charges, you need one Fe²⁺ ion and one SO₃²⁻ ion, resulting in the formula FeSO₃.