The number of unpaired electrons in $Ni(CO)_4$ is ..........

Give the correct sequence of initials $T$ or $F$ for the following statements. Use $T$ if the statement is true and $F$ if it is false.
$(I) \ Co(III)$ is stabilized in the presence of weak field ligands,while $Co(II)$ is stabilized in the presence of strong field ligands.
$(II)$ Four-coordinated complexes of $Pd(II)$ and $Pt(II)$ are diamagnetic and square planar.
$(III) \ [Ni(CN)_4]^{4-}$ ion and $[Ni(CO)_4]$ are diamagnetic tetrahedral and square planar respectively.
$(IV) \ Ni^{2+}$ ion does not form inner orbital octahedral complexes.

The metal $Ni$ $(Z = 28)$ combines with a unidentate ligand $X^-$ to form a paramagnetic complex $[NiX_4]^{2-}$. What are its geometry and the number of unpaired electrons in $Ni$?

Which complex has a square planar structure?

The $d$-electronic configuration of $[CoCl_4]^{2-}$ in a tetrahedral crystal field is $e^m t_2^n$. The sum of '$m$' and the number of unpaired electrons is $.............$.

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