The oxidation states of sulphur in the anions ${\mathrm{SO}}_3^{2-}$, ${\mathrm{S}}_2{\mathrm{O}}_4^{2-}$ and ${\mathrm{S}}_2{\mathrm{O}}_6^{2-}$  follow the order :

The oxidation states of Sulphur in the anions  ${\mathrm{S}}_2{\mathrm{O}}_4^{2-}$ and ${\mathrm{S}}_2{\mathrm{O}}_6^{2-}$ follow the order:

${\mathrm{S}}_2{\mathrm{O}}_4^{2-}<{\mathrm{SO}}_3^{2-}<{\mathrm{S}}_2{\mathrm{O}}_6^{2-}$.