Question

What is the average oxidation number of sulphur in tetrathionate ion?

Options

• 0

• +1.5

• +2.5

• +3.0

Answer 1

+2.5

Explanation:

In the structure of tetrathionate (S₄O₆^2-) ion, the oxidation number of each terminal S-atom is +5 and the oxidation number of each S-atom present at middle is 0. The total oxidation number of 4 S-atoms is +10.
Consequently, the average oxidation number is 
+10/4 = +2.5