Arrange the following in increasing order of ligand field strength.

A. \(CO\)

B. \(NH_3\)

C. \(EDTA^{4-}\)

D. \(Cl^-\)

E. \(I^-\)

Choose the correct answer from the options given below:

E, D, C, B, A

The correct answer is option 3. E, D, C, B, A.

To explain in detail, let's break down each ligand's effect on the ligand field strength and its position in the spectrochemical series:

Ligand field strength refers to the ability of a ligand to split the degenerate d-orbitals of a transition metal ion. The greater the splitting, the higher the energy difference between the d-orbitals, which affects the electronic transitions and colors of the complexes.

Spectrochemical series is a ranking of ligands based on their ability to cause splitting of d-orbitals in transition metal complexes. Ligands that produce larger d-orbital splitting are called strong field ligands, while those causing less splitting are called weak field ligands.

Ligands in the Given List

E. \(I^-\) (Iodide ion):

Nature: \(I^-\) is a large, weak field ligand.

Effect on d-Orbital Splitting: Causes minimal splitting of the d-orbitals, so it is at the end of the spectrochemical series.

Position in Series: Weakest ligand.

D. \(Cl^-\) (Chloride ion):

Nature: \(Cl^-\) is also a weak field ligand but slightly stronger than iodide.

Effect on d-Orbital Splitting: Causes more splitting than iodide but still relatively small compared to other ligands.

Position in Series: Stronger than \(I^-\), but weaker than other ligands listed here.

B. \(NH_3\) (Ammonia):

Nature: \(NH_3\) is a moderate field ligand.

Effect on d-Orbital Splitting: Causes a moderate amount of d-orbital splitting.

Position in Series: Stronger than \(Cl^-\) and \(I^-\), but weaker than chelating ligands like EDTA and strong field ligands like CO.

C. \(EDTA^{4-}\) (Ethylenediaminetetraacetate ion):

Nature: EDTA is a strong field ligand due to its chelating nature.

Effect on d-Orbital Splitting: Causes significant d-orbital splitting because it forms a stable chelate complex with the metal ion.

Position in Series: Stronger field ligand than \(NH_3\).

A.(CO\) (Carbon monoxide):

Nature: CO is a very strong field ligand.

Effect on d-Orbital Splitting: Causes the largest amount of d-orbital splitting, often leading to low spin complexes.

Position in Series: Strongest ligand listed here.

Spectrochemical Series Order: Based on their ability to split d-orbitals and their general properties:

Weakest Field Ligands: \(I^-\) < \(Cl^-\)

Moderate Field Ligand: \(NH_3\)

Strong Field Ligand: \(EDTA^{4-}\) < \(CO\)

Thus, the correct arrangement in increasing order of ligand field strength is: 3. E, D, C, B, A