To determine the properties of the complexes \([Ni(CO)_4]\) and \([NiCl_4]^{2-}\), we need to analyze their electronic configurations and types of bonding.
The electronic configuration of a Nickel (Ni) atom in its elemental form (atomic number 28) is:
\([Ar] \, 3d^8 \, 4s^2\)
In the formation of complexes, the oxidation state and the nature of ligands influence the electronic configuration.
\([Ni(CO)_4]\) is a complex where Ni is in the zero oxidation state. Carbon monoxide (CO) is a strong field ligand and causes the pairing of electrons in the 3d subshell.
\([NiCl_4]^{2-}\) is a complex where Ni is in the +2 oxidation state.
Based on the analysis, the correct property is:
Therefore, the correct option is: \([Ni(CO)_4]\) diamagnetic, \([NiCl_4]^{2-}\) paramagnetic.
In \([\text{Ni}(\text{CO})_4]\), nickel is in the zero oxidation state and has a \(3d^{10}\) electron configuration, leading to a fully paired electron configuration, making it diamagnetic.
In contrast, in \([\text{NiCl}_4]^{2-}\), nickel is in the \(+2\) oxidation state with a \(3d^8\) electron configuration. The chloride ligands are weak-field ligands and do not pair up the electrons, resulting in unpaired electrons and a paramagnetic nature.
Thus, the correct answer is:
\[ [\text{Ni}(\text{CO})_4] \text{ is diamagnetic and } [\text{NiCl}_4]^{2-} \text{ is paramagnetic.} \]What will be the equilibrium constant of the given reaction carried out in a \(5 \,L\) vessel and having equilibrium amounts of \(A_2\) and \(A\) as \(0.5\) mole and \(2 \times 10^{-6}\) mole respectively?
The reaction : \(A_2 \rightleftharpoons 2A\)

Cobalt chloride when dissolved in water forms pink colored complex $X$ which has octahedral geometry. This solution on treating with cone $HCl$ forms deep blue complex, $\underline{Y}$ which has a $\underline{Z}$ geometry $X, Y$ and $Z$, respectively, are
What will be the equilibrium constant of the given reaction carried out in a \(5 \,L\) vessel and having equilibrium amounts of \(A_2\) and \(A\) as \(0.5\) mole and \(2 \times 10^{-6}\) mole respectively?
The reaction : \(A_2 \rightleftharpoons 2A\)
A black body is at a temperature of 2880 K. The energy of radiation emitted by this body with wavelength between 499 nm and 500 nm is U1, between 999 nm and 1000 nm is U2 and between 1499 nm and 1500 nm is U3. The Wien's constant, b = 2.88×106 nm-K. Then,