The number of unpaired electrons in $[Co(NH_3)_6]^{3+}$ and $[CoF_6]^{3-}$ are respectively.....

What type of hybridisation is present in square planar geometry of complex $[Ni(CN)_4]^{2-}$?

Dimethyl glyoxime forms a square planar complex with $Ni^{2+}$. This complex should be

According to valence bond theory,the metal atom or ion can make use of which of the following orbitals to yield hybrid orbitals that can form bonds with ligands?

Addition of excess aqueous ammonia to a pink coloured aqueous solution of $MCl_2 \cdot 6H_2O (X)$ and $NH_4Cl$ gives an octahedral complex $Y$ in the presence of air. In aqueous solution,complex $Y$ behaves as a $1:3$ electrolyte. The reaction of $X$ with excess $HCl$ at room temperature results in the formation of a blue coloured complex $Z$. The calculated spin-only magnetic moment of $X$ and $Z$ is $3.87 \ B.M.$,whereas it is zero for complex $Y$.
Among the following options,which statement$(s)$ is(are) correct?
$[A]$ The hybridization of the central metal ion in $Y$ is $d^2sp^3$
$[B]$ $Z$ is a tetrahedral complex
$[C]$ Addition of silver nitrate to $Y$ gives only two equivalents of silver chloride
$[D]$ When $X$ and $Z$ are in equilibrium at $0^{\circ}C$,the colour of the solution is pink

What is the geometry of $[Ni(CO)_4]$?