Why `E^(-)` values for Mn, Ni and Zn are more negative than expected?

Explanation

Negative values of `Mn^(2+)` and `Zn^(2+)` are related to stabilities of half-filled and completely filled configuration respectively. But for `Ni^(2+)`, `E^(@)` value is related to the highest negative enthalpy of hydration
Hence, `E^(Theta)` values for Mn, Ni and Zn are more negative than expected.