Sulfite ion
Charge: 2- · Type: Polyatomic anion · Molar mass: 80.057 g/mol
Made of: sulfur, oxygen
How it forms
Sulfurous acid loses two protons to give SO3^2-. Unlike sulfate, the sulfur atom keeps a lone pair of electrons, which makes sulfite a reducing agent that reacts readily with oxygen.
Naming note
SO3^2- is the sulfite ion; SO4^2- is sulfate. The -ite ending marks the ion with fewer oxygen atoms.
Examples in compounds
Sodium sulfite
Calcium sulfite
Potassium sulfite