Question

The correct sequence of ligands in the order of decreasing field strength is :

• A. $\text{CO} > \text{H}_2\text{O} > \text{F}^- > \text{S}^{2-}$
• B. $\text{OH}^- > \text{F}^- > \text{NH}_3 > \text{CN}^-$
• C. $\text{NCS}^- > \text{EDTA}^{4-} > \text{CN}^- > \text{CO}$
• D. $\text{S}^{2-} > \text{OH}^- > \text{EDTA}^{4-} > \text{CO}$

Answer 1

The Correct Option is A

Understanding Ligand Field Strength:

The strength of a ligand in the context of field strength refers to its ability to split the $d$-orbitals of a transition metal ion, which affects the color, magnetic properties, and stability of the metal complex. Ligands are arranged according to their field strength in the Spectrochemical Series.

Spectrochemical Series:

According to the Spectrochemical Series, ligands are arranged in the following order of increasing field strength:

$$I^- < \text{Br}^- < S^{2-} < \text{Cl}^- < \text{F}^- < \text{OH}^- < \text{H}_2\text{O} < \text{NCS}^- < \text{EDTA}^{4-} < \text{NH}_3 < \text{en} < \text{CN}^- < \text{CO}$$

Arrange the Given Ligands in Decreasing Field Strength:

From the Spectrochemical Series:

$$\text{CO} > \text{H}_2\text{O} > \text{F}^- > S^{2-}$$

Conclusion:

The correct sequence in the order of decreasing field strength is:

$$\text{CO} > \text{H}_2\text{O} > \text{F}^- > S^{2-}$$

which corresponds to Option (1).