Question

What is the crystal field stabilization energy (CFSE) of $\left[Fe\right(H_{2}O{)}_6{]}^{2+}$?

• A. $-0.4{\Delta }_o$
• B. $0.4{\Delta }_o$
• C. $-2.4{\Delta }_o$
• D. $2.4{\Delta }_o$

Answer 1

The correct option is A $-0.4{\Delta }_o$

Given complex is:
$\left[Fe\right(H_{2}O{)}_6{]}^{2+}$
$\text{The electronic configuration of}F{e}^{2+}:\left[Ar\right]3d^6$
Since, $H_{2}O$ is a weak field ligand hence, it will not pair up the electrons .
$\therefore \text{The electronic configuration will be:}{t}_{2g}^4{e}_g^2$
${\text{CFSE}}_{\text{octahedral}}=-0.4{\Delta }_o{n}_{\left(t_{2g}\right)}+0.6{\Delta }_o{n}_{\left(e_g\right)}$
$\Rightarrow {\text{CFSE}}_{\text{octahedral}}=-0.4{\Delta }_o\times 4+0.6{\Delta }_o\times 2$
$\Rightarrow {\text{CFSE}}_{\text{octahedral}}=-1.6{\Delta }_o+1.2{\Delta }_o=-0.4{\Delta }_o$