Question

Give reasons:
Third ionization enthalpy of manganese is unusually high.

Answer 1

It's valence configuration of $Mn$ is,

$4s^{2}3d^5$ implies we should remove from the $2e^{-}$ from $4s^2$ then comes $3d^5$ which is half filled configuration. It is stable configuration due to greater exchange energy and hence high energy is needed to remove an $e^{-}$ from this configuration.

Hence third ionization enthalpy of Manganese is unusually high.