Question

The complex $CoC{l}_4^{2-}$ has a tetrahedral structure. How many $d-$ electrons are on the cobalt?

Answer 1

Atomic no. of cobalt is 27. Outermost shell has $3d^7,4s^2$.In the complex $Co$ is in $+2$ state so it has 7 $d$-−electrons are on the outermost shell of cobalt.