Question

Increasing order of crystal field splitting power of the following ligands:
(A) CN$^-$
(B) Cl$^-$
(C) F$^-$
(D) H$_2$O
Choose the correct answer from the options given below:

• A. A $<$ B $<$ C $<$ D
• B. A $<$ C $<$ B $<$ D
• C. A $<$ D $<$ C $<$ B
• D. B $<$ C $<$ D $<$ A

Answer 1

The Correct Option is D

The crystal field splitting power of ligands is determined by their ability to split the d-orbitals of a central metal ion in a coordination complex. Strong field ligands cause a large split, whereas weak field ligands cause a smaller split. This property is related to the strength of the ligand in forming a coordinate bond with the metal ion.

The order of ligands in terms of increasing crystal field splitting power is determined by their position in the spectrochemical series. The typical order for the ligands given is: Cl^- < F^- < H₂O < CN^-.

Ligand	Crystal Field Splitting Power
Cl-	Weak
F-	Weak-Moderate
H2O	Moderate
CN-	Strong

Thus, the correct increasing order of crystal field splitting power of the given ligands is B < C < D < A.

Answer 2

Ligands are classified as strong or weak field ligands based on their ability to split the d-orbital energies in a metal complex. Cl⁻ is a weak field ligand, followed by F⁻, H₂O (which is a moderate field ligand), and CN⁻ is a strong field ligand. The classification depends on how strongly the ligands interact with the central metal ion and affect its electron configuration.

In general, strong field ligands like CN⁻ cause a large splitting of the d-orbital energies, resulting in low-spin complexes. These ligands typically create a larger crystal field splitting energy (Δ_o), which can lead to the pairing of electrons. On the other hand, weak field ligands like Cl⁻ cause a small splitting of the d-orbital energies, leading to high-spin complexes, where electrons tend to remain unpaired.

Water (H₂O) is considered a moderate field ligand, and it falls in between the weak and strong field categories. It causes some splitting but not as much as strong field ligands like CN⁻. The behavior of ligands can significantly influence the properties of the resulting complex, such as its magnetic behavior, color, and stability.

This leads to the increasing order of crystal field splitting power:

\(Cl^− \, (C) \, < F^− \, (D) \, < H_2O \, (A) \, < CN^− \, (B)\)