# How many unpaired electrons in ["Co"("CN")_6]^(3-)?

$\text{The number is ZERO...........}$
$C {o}^{3 +}$ has a ${d}^{6}$ electronic configuration.......and these are classically LOW SPIN, especially with strong field ligands such as cyanide.........
${\left[C o {\left(C \equiv N\right)}_{6}\right]}^{3 -}$ is thus diamagnetic with no unpaired electrons.