Dear Student,
Please find below the solution to your problem.
Reducing power is the ability of a chemical to reduce other substances, or the environment. and reduce to other substances means addition of hydrogen and removal of oxygen and also gain of electron , the reducing power is increasing when going down the group reducing power has to deal with its reactivity, that is the ease at the atom to be oxidies to form cation. since going down the group, the size of atom increase, causing the attraction of the nucleus towards the valence electrons weaker, which accounts for higher reactivity
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