Let us assign electrons in the d
orbitals of metal ion in octahedral coordination entities Obviously,
dthe single d electron occupies one of the lower energy t2g orbitals In
2 and d
3 coordination entities, the d electrons occupy the t2g orbitals
singly in accordance with the Hund’s rule For d
4 ions, two possible
patterns of electron distribution arise: (i) the fourth electron could
either enter the t2g level and pair with an existing electron, or (ii) it
could avoid paying the price of the pairing energy by occupying the
eg level