Question

Identify a ligand with highest field strength among the following.

• A. \(\text{H}_2\text{O}\)
• B. \(\text{NH}_3\)
• C. \(\text{S}^{2-}\)
• D. \(\text{NCS}^-\)

Hint:

Use the spectrochemical series.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Ligand field strength tells how strongly a ligand splits the d orbitals of the metal. It is ranked in the spectrochemical series, from weak to strong.

Step 2: Key Formula or Approach:
Spectrochemical series (part): \(\text{I}^- < \text{Br}^- < \text{S}^{2-} < \text{SCN}^- < \text{Cl}^- < \text{F}^- < \text{OH}^- < \text{H}_2\text{O} < \text{NCS}^- < \text{NH}_3 < \text{en} < \text{CN}^- < \text{CO}\).

Step 3: Detailed Explanation:
Among the four given ligands, \(\text{S}^{2-}\) sits near the weak end. The N-bonded \(\text{NCS}^-\) and \(\text{H}_2\text{O}\) are in the middle, and \(\text{NH}_3\) comes after both.
So the strongest field ligand here is \(\text{NH}_3\), a neutral N-donor that is also a good sigma donor.

Final Answer:
\(\text{NH}_3\) is the strongest field ligand of the four, option (B). \[ \boxed{\text{NH}_3} \]