Fe(Z=26)=[Ar]4s23d6 (∴ Highest oxidation state of Fe is +3) Mn(Z=25)=[Ar]4s23d5 (5 unpaired electrons in 3d-orbital and 2e−in 4s.) Mn can show 6 oxidation states from MnO to MnO4−. Cr(Z=24)=[Ar]4s13d5 (∴ Highest oxidation state of Cr is +3) V(Z=23)=[Ar]3d34s2 ( ∴ Highest oxidation state of V is +2) Hence, greatest number of oxidation state is shown by Mn.
