`E^(0)` values of Mn, Ni and Zn are more negative than expected from general trend. This is due to the stabilities of half filled d-subshell `(d^(5))" in "Mn^(+2)` and completely filled d-subshell `(d^(10))` in Zinc. For Nickel `E^(0)` value is related to the highest negative enthalpy of hydration.
