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

Low spin complex of $d^6$-cation in an octahedral field will have the following energy $\left(\Delta_o=\right.$ crystal field splitting energy in an octahedral field, $P=$ electron pairing energy)
  1. $\frac{-12}{5} \Delta_o+P$
  2. $\frac{-12}{5} \Delta_o+3 P$
  3. $\frac{-2}{5} \Delta_o+2 P$
  4. $\frac{-2}{5} \Delta_o+P$

Solution

\(\text {C.F.S.E. }=(-0.4 x+0.6 y) \Delta_o+z P\)
where \(\mathrm{x}=\) number of electrons occupying \(\mathrm{t}_{2 g}\) orbital
\(y=\) number of electrons occupying \(e_g\) orbital
\(z=\) number of pairs of electrons
For low spin \(\mathrm{d}^6\) complex electronic configuration
\(\begin{aligned}
& =t_{2 g}^6 e_g^0 \text { or } t_{2 g}^{2,2,2} e_g^0 \\
& \therefore \quad x=6, y=0, z=3 \\
& \text { C.F.S.E. }=(-0.4 \times 6+0 \times 0.6) \Delta_o+3 P \\
& =\frac{-12}{5} \Delta_o+3 P
\end{aligned}\)

Asked in: NEET 2012 (Mains)

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