In KMnO4, oxidation state of Mn is +7.
As the oxidation state of atom increases, the element become more electronegative in nature.
Mn gain 5 electron in acidic medium and reduces to +2 oxidation state.
Gain of 5 electron shows that the electronegativity of Mn has increased.
Therefore, KMnO4 is a good oxidizing agent.
Note: Change of oxidation state of Mn is as:
Acidic medium: +7 to +2
Basic medium: +7 to +4
Neutral medium: +7 to +6
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