The number of unpaired electrons in the complex ion ${\left[Co{F}_6\right]}^{3-}$ is

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.