What is the number of $d$-electrons in the metal ion of the tetrahedral complex $K_2[NiCl_4]$?

The number of unpaired electrons responsible for the paramagnetic nature of the following complex species are respectively $:$
$[Fe(CN)_6]^{3-}, [FeF_6]^{3-}, [CoF_6]^{3-}, [Mn(CN)_6]^{3-}$

$[PdCl_2(PMe_3)_2]$ is a diamagnetic complex of $Pd(II)$. How many unpaired electrons are present in the analogous complex of $Ni(II)$?

In the extraction of silver,zinc metal is used as a reducing agent. What is the molecular structure of the zinc complex formed in this reaction?

Identify the type of hybridization involved in the hexaamminecobalt$(III)$ complex ion.

The geometry and the number of unpaired electron$(s)$ of $[MnBr_4]^{2-}$,respectively,are