Question

Third ionisation enthalpy of mn (at no. 25) is very high?

Answer 1

Mn =1s^2 2s^2 2p^6 3s^2 3p^6 3d^5 4s^2
Mn^2+ =1s^2 2s^2 2p^6 3s^2 3p^6 3d^5 4s^0
when Mn^2+ is convert to Mn^3+ ion by oxcidation then the ionisation enthalpy of Mn is high. Because in this time the electronic configurations of Mn is 3d^5 4s^0. d orbital is half field and this is most stable. when Mn^2+ ion oxcidised then the electronic configurations of Mn is 3d^4 4s^0. For this process highly heat generated. then the third ionisation enthalphy of Mn is high.