If an element is in its highest possible oxidation state in a compound, it can act only as an oxidising agent, for example, KMnO4 , K2Cr2O7 , HNO3 , H2SO4 , HCIO4 etc.
If element is in its lowest oxidation state in a compound, it can act only as a reducing agent. For example, H2S, H2C2O4 , FeSO4 , Na2S2O3 , SO2 , SnCI2 , many metals etc.
The strength of oxyacids of chlorine decrease in the order. HCIO4 > HCIO3 > HCIO2 > HCIO
If an element is in intermediate oxidation state in a compound, it can act both as an oxidising as well as a reducing agent. For example, H2O2 , H2SO3 , HNO3 , SO2 etc.
