Question

Maximum value of paramagnetism is shown by

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

Answer 1

Answer: (B)

Paramagnetism is shown due to unpaired electrons. Since, $C{N}^{-}$ is a strong field ligand, it causes pairing of electrons.
$(a)$ In $[Fe(CN{)}_6{]}^{3-},F{e}^{3+}=Ar[3d^5]$

$1$ unpaired electron
$(b)$ In $[Cr(CN{)}_6{]}^{3-},C{r}^{3+}=Ar[3d^3]$

$3$ unpaired electrons.
$(c)$ In $[Co(CN{)}_6{]}^{3-},C{o}^{3+}=Ar[3d^6]$

No unpaired electron.
$(d)$ In $[Sc(CN{)}_6{]}^3,S{c}^{3+}=Ar[3d{]}^{\circ }$

No unpaired electron.
Hence, $[Cr(CN{)}_6{]}^{3-}$ will show maximum paramagnetism.