Question

Assertion (A) : ${\left[Co{F}_6\right]}^{3-}$ is paramagnetic.
Reason (R) : $C{o}^{3+}$ has $3d^6$ outer electronic configuration. The unpaired electrons do not pair up because of weak field provided by $F^{-}$.

• A. A and R both are correct and R is the correct explanation of A.
• B. A and R both are correct but R is not the correct explanation of A.
• C. A is incorrect while R is correct.
• D. A and R both are incorrect.

Answer 1

Answer: (A)

In complex ${\left[Co{F}_6\right]}^{3-}$ oxidation number of $Co=+3$
Electronic configuration of
$C{o}^{3+}=1s^2,2s^2,2p^6,3s^2,3p^6,3d^6$

In $C{o}^{3+}$ number of unpaired electrons is four, is the ligand of weak field. Hence it doesn't paired up electrons of $d$-orbital.
So, In ${\left[Co{F}_6\right]}^{3-}$

So, ${\left[Co{F}_6\right]}^{3-}$ is paramagnetic.
$C{o}^{3+}$ has $3d^6$ outer electronic configuration, but four unpaired electrons don't pair up because of weak field provided by $F^{-}$.
Hence, assertion is correct and reason is the correct explanation of assertion