Chemistry - Coordination Chemistry Question with Solution | TestHub

For a $3d^6$ configuration in an octahedral field:

Strong field ligand (low spin): $t_{2g}^6{e}_g^0$. CFSE = $6(-0.4{\Delta }_o)+0(0.6{\Delta }_o)=-2.4{\Delta }_o$. So $x=-2.4$.

Weak field ligand (high spin): $t_{2g}^4{e}_g^2$. CFSE = $4(-0.4{\Delta }_o)+2(0.6{\Delta }_o)=-1.6{\Delta }_o+1.2{\Delta }_o=-0.4{\Delta }_o$. So $y=-0.4$.

Therefore, $x+y=-2.4+(-0.4)=-2.8$.