Question

$[Co{F}_6{]}^{3-}$ is a coordination complex ion.

State the magnetic behaviour of the complex.

Answer 1

$[Co{F}_6{]}^{3-}$ is a paramagnetic complex ion due to presence of 4 unpaired electrons.
$C{o}^{3+}$ ion has $3d^6$ outer electronic configuration with 4 unpaired electrons.
Note:
In the complex $[Co{F}_6{]}^{3-}$, the oxidation number of Co is +3. The outer electronic configuration of $C{o}^{3+}$ ion is $3d^6$. It can also be written as $t_{2g}^4{e}_g^2$. Thus there are 4 unpaired electrons, 2 in $t_{2g}$ level and 2 in $e_g$ level.