Low spin complex of `d^6`-cation in an octahedral field will have the following energy:

Options

A. `(-12)/(5) Delta_0 + P`
B. `(-12)/(5) Delta_0 + 3P`
C. `(-2)/(5) Delta_0 + 2P`
D. `(-2)/(5) Delta_0 + P`

Answer

B

Explanation

If the energy separation for octahedral complex is `Delta_0` and the required pairing energy is P then : In crystal field splitting, for strong field ligand,`Delta_0 gt P` , so it becomes more energetically favourable for the fourth electron to occupy a `t_(2g)` orbital with configuration `t_(2g)^4 e_g^0`. Similarly for a `d^6` configuration (for forming a low – spin complex), electron will favour the following configuration :

For three `t_(eg)` orbitals energy will decrease by 2/5 `Delta_0` for each electron. The required pairing energy for 3 pairs of electrons = 3P
Total energy = `3P - 6(2//5)Delta_0 = (-12//5)Delta_0 + 3P` .