(a) Transition metals are able to form complex compounds due to the small size of metal, high ionic charge and availability of vacant d-orbital.
(b) E∘ values of (Mn2+∕Mn) and (Zn2+∕Zn) are more negative than expected due to the greater stability of half filled d-subshell of Mn2+(3d5) and completely filled d-subshell of Zn2+(3d10).
(c) Due to a very small energy gap between 5f,6d and 7 s-subshells resulting in easier excitation of the outermost electrons to higher energy levels.