A substance contains an element at its probable maximum oxidation number , does this substance have a maximum chance to be an oxidizing agent or have a minimum chance to be a reducing agent ?
Just think of an example of an element in a compound with the element at its max oxidation state. For example take SO3 where S is +6. It CAN'T be oxidized any further (if this is the max) to go to S7 or S8 or higher) but it can go down to something like SO2 or S or H2S.
So if it goes from +6 to say +4 it had to gain electrons which makes it reduced which makes it an oxidizing agent.
