In sulphur dioxide `(SO_(2))` , the oxidation number (O.N) of S is +4 and the range of the O.N. that S can have is from + 6 to -2 .

Therefore , `SO_(2)` can act as an oxidising as well as a reducing agent .

In hydrogen peroxide `(H_(2)O_(2))`, the O.N. of O is –1 and the range of the O.N. that O can have is from 0 to –2. O can sometimes also attain the oxidation numbers +1 and +2. Hence, `H_(2)O_(2)` can act as an oxidising as well as a reducing agent

In ozone `(O_(3))`, the O.N. of O is zero and the range of the O.N. that O can have is from 0 to –2. Therefore, the O.N. of O can only decrease in this case. Hence, `O_(3)` acts only as an oxidant.

In nitric acid `(HNO_(3))`, the O.N. of N is +5 and the range of the O.N. that N can have is from +5 to –3. Therefore, the O.N. of N can only decrease in this case. Hence, `HNO_(3)` acts only as an oxidant.