If CFSE ( Crystal field splitting energy) has lower value than the pairing energy for an octahedral complex with d4 then the electronic configuration of the ion will be:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → t2g3eg1
In an octahedral complex the d orbitals split into three lower t2g orbitals and two higher eg orbitals, separated by the crystal field splitting energy Δo. The first three electrons of a d4 ion go singly into t2g.
Here the splitting energy is lower than the pairing energy, so the d4 ion has the high spin configuration t2g3eg1.
Why the other options are incorrect
Option (1) t2g1eg3 — Incorrect. Electrons would fill the higher eg set while t2g orbitals are still empty, which never happens.
Option (3) t2g2eg2 — Incorrect. One t2g orbital would stay empty while two electrons sit in eg; the lower set is filled singly first.
Option (4) t2g4eg0 — Incorrect. This low spin configuration forms only when Δo > P.
NCERT (2026-27 edition):
Crystal Field Theory – …
