The spin only magnetic moment value for the complex ${\left[Co{\left(CN\right)}_6\right]}^{4-}$  is________ BM.

$ln{\left[Co{\left(CN\right)}_6\right]}^{4-},$ Co has +2 oxidation state

Hence, electronic configuration of CO2+ is $\left[Ar\right]3d^{7}4s^0$ ${}^{}{}^{}$ . In complex   ${\left[Co{\left(CN\right)}_6\right]}^{4-},$ ${{}_{}}^{}$given ligand CN is strong hence, after pairing in d-subshell, total number of unpaired electron =

$\therefore$ spin magnetic moment =   $\sqrt[]{1\left(1+2\right)}=\sqrt[]{3}=1.73BM$ $\text{exception 25:}\text{exception 25:}$

$=1.73BM\approx 2.0BM$