Chemistry - Coordination Chemistry Question with Solution | TestHub

In an octahedral field, $t_{2g}$ orbitals are occupied first (lower energy). Whether they are fully used depends on electron configuration and pairing energy.

(a) d⁶, CFSE > PE (strong field) → low spin: $t_{2g}{}^6{e}_g{}^0$

(b) d⁶, CFSE < PE (weak field)→ high spin: $t_{2g}{}^4{e}_g{}^2$ but still $t_{2g}$ present (not fully stabilized case asked in concept key)

(c) d⁸, CFSE < PE→ $t_{2g}{}^6{e}_g{}^2$, $t_{2g}$ present

(d) d⁵, CFSE < PE→ $t_{2g}{}^3{e}_g{}^2$, but question key focuses on required condition set

Standard exam key: (a) and (c).