d
Key ldea In case of high spin complex, \(\Delta_{0}\) is small. Thus, the energy required to pair up the fourth electron with the

electrons of lower energy d-orbitals would be higher than that required to place the electrons in the higher d-orbital.

Thus, pairing does not occur.

For high spin \(d^{4}\) octahedral complex Crystal fleld stabilisation energy

\(=(-3 \times 0.4+1 \times 0.6) \Delta_{0}\)

\(=(-1.2+0.6) \Delta_{0}=-0.6 \Delta_{0}\)