Question

What is CFSE of complex ion $[Fe{F}_6{]}^{4-}$ in terms of ${\Delta }_o$?

• A. -0.4
• B. 0.4
• C. -0.6
• D. 0.6

Answer 1

The correct option is A -0.4

Fe is in +2 state in $[Fe{F}_6{]}^{4-}$

$Fe-\left[Ar\right]4s^{2}3d^6$

$F{e}^{2+}-\left[Ar\right]3d^6$

Since $F^{-}$ is a weak ligand according to CFSE theory there will be 4 electrons in three $t_{2g}$ orbital and 2 electrons in two $e_g$ level.

CFSE= [(-0.4)4 + (0.6)2]${\Delta }_o$= -0.4${\Delta }_o$