Question

Which of the following statements is incorrect?

Answer 1

Hint: We can find the hybridization of the above given complexes using the valence bond theory. Now identify if the ligands are strong field ligands or weak field ligands. From this you can find the shape of the complex compound. Using the above data you can find if the complex is paramagnetic or diamagnetic.


Complete step-by-step answer:
According to valence bond theory, electrons in a molecule occupy atomic orbitals and not molecular orbitals. The atomic orbitals overlap on the bond formation and the strength of the bond depends on the extent of overlap.

Postulates of Valence Bond Theory:
- Covalent bonds are formed when two valence orbitals belonging to two different atoms overlap onto each other. Due to overlapping the electron density in that region increases, thereby increasing the stability of the molecule thus formed.
- The presence of many unpaired electrons in the valence shell of an atom enables the atoms to form multiple bonds with each other. However, the paired electrons present in the valent shell do not take part in formation of chemical bonds.
- Covalent bonds are directional and parallel to the region corresponding to atomic orbitals that are going to overlap.
- Sigma bonds and pi bonds differ in the pattern that the atomic orbitals overlap in, i.e. sigma bonds undergo head on overlap however pi bonds undergo sideways overlapping.
Magnetic moment: $\sqrt{n(n+2)}$
Where,
n is the number of unpaired electrons
We will now calculate the magnetic moment of ${{K}_{4}}[Ni{{(CN)}_{4}}]$ and ${{K}_{4}}[Ni{{(Cl)}_{4}}]$.
${{K}_{4}}[Ni{{(CN)}_{4}}]$:
Oxidation state of Ni = 0
Electronic configuration : $1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{s}^{2}}3{{p}^{6}}4{{s}^{2}}3{{d}^{8}}$
There are 2 unpaired electrons in the 3d subshell. Hence the complex compound is paramagnetic in nature having 2 unpaired electrons.
${{K}_{4}}[Ni{{(Cl)}_{4}}]$:
Oxidation state of Ni = 0
Electronic configuration : $1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{s}^{2}}3{{p}^{6}}4{{s}^{2}}3{{d}^{8}}$
There are 2 unpaired electrons in the 3d subshell. Hence the complex compound is paramagnetic in nature having 2 unpaired electrons.
However, our above observation is different from the answer mentioned in options (B) and (C).

Therefore, the incorrect answers are options (B) and (C).


Note: Valence bond theory was successful in determining the hybridization of atoms in a molecule. However, the theory had some limitations ,like:
- Unable to explain the tetravalency of carbon
- No insight or information on the energies of electrons
- Incorrect assumption that electrons are localized in specific areas only
- No distinction between weak and strong ligands ( hybridization of complex compounds)