Sulfites are chemical compounds that have the sulfite ion which is SO3-- with a valence of 2-.
Iron can form chemicals in which it is capable of existing in many oxidation states ranging from -2 to +6. Most naturally occurring compounds of iron have iron exhibiting a valence of 2+ or 3+. Iron(II) sulfite is a compound with the chemical formula FeSO3. Here iron has a valence of 2+ and the sulfite ion exhibits a valence of 2-. Like most sulfates and sulfites of iron iron(II) sulfite is also found in the anhydrous state as a crystal formed with water molecules.