b
n the 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,

therefore, Crystal field stabilisation energy

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

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

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