The largest oxidation number exhibited by an element depends on its electronic configuration. With which of the following electronic configurations will the element exhibit the largest oxidation number?
Hint: In case of d block elements, both (n-1)d and ns orbital electrons participate in bond formation
Highest oxidation number of any transition element = (n-1)d electrons + ns electrons.
Therefore, large the number of electrons in the 3d-orbitals, higher is the maximum oxidation.