Why is the third ionisation energy of Manganese (Z = 2525 ) is unexpectedly high?
Manganese has an atomic number of 2525 and an electronic configuration of [Ar]4s2,3d5[Ar]4s2,3d5 . The loss of two electrons transforms Mn2 + Mn2 + into [Ar]3d5[Ar]3d5 , a structure with a half-filled d-orbital that is exceedingly stable. As the third electron must be removed from the stable configuration of Mn2 + Mn2 + , the third ionisation energy is extremely large.
