These elements show variable oxidation states because their valence electrons are in two different sets of orbitals, that is (n-1)d and ns. The energy difference between these orbitals is very less, so both the energy levels can be used for bond formation. Thus, transition elements have variable oxidation states.
Mn−3d54s2 configuration shows highest oxidation state +7.
Transition metals can have multiple oxidation states because of their electrons. The transition metals have several electrons with similar energies, so one or all of them can be removed, depending the circumstances. This results in different oxidation states.
To find the highest oxidation state in non-metals, from the number 8 subtract the number of the group in which the element is located, and the highest oxidation state with a plus sign will be equal to the number of electrons on the outer layer.
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