Write the structure and oxidation numbers of sulphur in tetrathionic acid.

Explanation

`HO-overset(O)overset(||)underset(O)underset(||)S-S-overset(O)overset(||)underset(O)underset(||)S-OH` (or) tetrathionate `.^(-)O-overset(O)overset(||)underset(O)underset(||)S-S-S-overset(O)overset(||)underset(O)underset(||)S-O^(-)`
Tetrathionic acid or its salt tetrathionate has persulphide link, `S-S`.
The oxidation states of sulphur are: `+5, 0, 0 and +5`.
The average oxidation state of Sis `+2.5`.