Question

The number of unpaired electrons in the complex ion ${\left[Co{F}_6\right]}^{3-}$ is
(At. no. of $Co=27$ )

• A. 3
• B. 2
• C. 4
• D. 0

Answer 1

Answer: (C)

In complex ion ${\left[Co{F}_6\right]}^{3-},Co$ is present in $+3$ oxidation state
${}_{27}Co=1s^2,2s^{2}2p^6,3s^{2}3p^{6}3d^7,4s^2$
$C{o}^{3+}=1s^2,2s^{2}2p^6,3s^{2}3p^{6}3d^6$
Therefore, the number of unpaired electrons in $3d$ subshell of ${\left[Co{F}_6\right]}^{3-}$ is $4$ .