Question

Arrange the following cyano complexes in decreasing order of their magnetic moment.

• A. ${\left[Cr(CN{)}_6\right]}^{3-}>{\left[Mn(CN{)}_6\right]}^{3-}>{\left[Fe(CN{)}_6\right]}^{3-}>{\left[Co(CN{)}_6\right]}^{3-}$
• B. ${\left[Mn(CN{)}_6\right]}^{3-}>{\left[Cr(CN{)}_6\right]}^{3-}>{\left[Fe(CN{)}_6\right]}^{3-}>{\left[Co(CN{)}_6\right]}^{3-}$
• C. ${\left[Fe(CN{)}_6\right]}^{3-}>{\left[Cr(CN{)}_6\right]}^{3-}>{\left[Mn(CN{)}_6\right]}^{3-}>{\left[Co(CN{)}_6\right]}^{3-}$
• D. ${\left[Co(CN{)}_6\right]}^{3-}>{\left[Cr(CN{)}_6\right]}^{3-}>{\left[Mn(CN{)}_6\right]}^{3-}>{\left[Fe(CN{)}_6\right]}^{3-}$

Answer 1

Answer: (A)

${\left[Cr(CN{)}_6\right]}^{3-}C{r}^{3+}$ in strong ligand field $=t_{2g}^3{e}_g^0=3$ unpaired electron

- ${\left[Mn(CN{)}_6\right]}^{3-}M{n}^{3+}$ in strong ligand field $=t_{2g}^4{e}_g^0=2$ unpaired electron

- ${\left[Fe(CN{)}_6\right]}^{3-}F{e}^{3+}$ in strong ligand field $=t_{2g}^5{e}_g^0=1$ unpaired electron

${\left[Co(CN{)}_6\right]}^{3-}C{o}^{3+}$ in strong ligand field $=t_{2g}^6{e}_g^0=0$ unpaired electron