Why is the 3rd ionization energy of Mn (Z = 25) is unexpectedly high ?

Why is the third ionization energy of manganese (at no 25) unexpectedly high?

Why is the third ionisation energy of manganese (At No. 25) unexpectedly high?

Why is the third ionization enthalpy of manganese (At. no.=25) unexpectedly high ?

Why the third ionization energy of manganese (atomic number 25) unexpectedly high?

Why is the third ionisation energy of manganese exceptionally high ?

How would you account for the following ? The third ionization enthalpy of manganese (Z = 25) is exceptionally high.

Ionization energy is high for

Assign a reason for each of the following: The third ionization enthalpy of Mn (Z = 25) is higher than that of either Cr (Z = 24) or Fe (Z = 26).