Question

Low spin complex of $d^6-$ cation in an octahedral field will have the following energy:
$({\Delta }_0=$ crystal feild splitting energy in an octahedral feild, P= Electron pairing energy$)$

• A. $\frac{-12}{5}{\Delta }_0+P$
• B. $\frac{-12}{5}{\Delta }_0+3P$
• C. $\frac{-2}{5}{\Delta }_0+2P$
• D. $\frac{-2}{5}{\Delta }_0+P$

Answer 1

The correct option is B $\frac{-12}{5}{\Delta }_0+3P$

$(CFSE=-0.4x+0.6y){\Delta }_0+zP$
Where, $x=\text{number of electrons occupying}{t}_{2g}\text{orbitals}$
$y=\text{number of electrons occupying}{e}_g\text{orbital}\text{z= number of pairs of electrons}$
For low spin $d^6$ complex electronic configuration

$=t_{2g}^6{e}_g^0\text{or}{t}_{2g}^{2,2,2}{e}_g^0$

$\therefore x=6,y=0,z=3$
$\text{CFSE}=(-0.4\times 6+0\times 0.6){\Delta }_0+3P$
$=\frac{-12}{5}{\Delta }_0+3P$