The tetrathionate anion, S4O62−, is a sulfur oxoanion derived from the compound tetrathionic acid, H2S4O6. Two of the sulfur atoms present in the ion are in oxidation state 0 and two are in oxidation state +5. Alternatively, the compound can be viewed as the adduct resulting from the binding of the Lewis base S22− to SO3. Tetrathionate is one of the polythionates, a family of anions with the formula [Sn(SO3)2]2−. It's IUPAC name is (sulfonatodisulfanyl)sulfonate, the name of i… (More on Tetrathionate)