Looking for classes? Ksquare Career Institute, Bengaluru →
Which of these statements about $[Co(CN)_6]^{3-}$ is true?
A
$[Co(CN)_6]^{3-}$ has no unpaired electrons and will be in a low-spin configuration
B
$[Co(CN)_6]^{3-}$ has four unpaired electrons and will be in a low-spin configuration
C
$[Co(CN)_6]^{3-}$ has four unpaired electrons and will be in a high-spin configuration
D
$[Co(CN)_6]^{3-}$ has no unpaired electrons and will be in a high-spin configuration
Detailed Solution
$Co^{3+}$: $[Ar]3d^6$
$CN^-$ is a strong field ligand, so $\Delta_o$ is large and the electrons pair up in the $t_{2g}$ level.
[add image: $3d^6$ splitting into $t_{2g}^6 e_g^0$ under a strong field]
Configuration $t_{2g}^6e_g^0$: no unpaired electrons, low-spin complex.
$CN^-$ is a strong field ligand, so $\Delta_o$ is large and the electrons pair up in the $t_{2g}$ level.
[add image: $3d^6$ splitting into $t_{2g}^6 e_g^0$ under a strong field]
Configuration $t_{2g}^6e_g^0$: no unpaired electrons, low-spin complex.