Question

A ligand can also be regarded as

• A. Lewis acid
• B. Bronsted base
• C. Lewis base
• D. Bronsted acid

Hint:

In coordination compounds, ligand is a Lewis base and central metal ion is a Lewis acid.

Answer 1

The Correct Option is C

Concept:
A ligand is an ion or molecule that donates a pair of electrons to a central metal atom or ion to form a coordinate bond. According to Lewis concept: \[ \text{Lewis acid} = \text{electron pair acceptor} \] \[ \text{Lewis base} = \text{electron pair donor} \]

Step 1: Understand ligand behavior.
Ligands have lone pairs of electrons. For example: \[ NH_3,\ H_2O,\ Cl^-,\ CN^- \] These species donate electron pairs to metal ions.

Step 2: Understand metal ion behavior.
The central metal ion accepts electron pairs from ligands. So the metal ion behaves as: \[ \text{Lewis acid} \] The ligand donates electron pairs. So the ligand behaves as: \[ \text{Lewis base} \]

Step 3: Check the options.
Option (A) Lewis acid is incorrect because ligand donates, not accepts, electron pairs.
Option (B) Bronsted base accepts proton, but coordination bonding is better explained by Lewis concept.
Option (C) Lewis base is correct.
Option (D) Bronsted acid is incorrect. Hence, the correct answer is: \[ \boxed{(C)\ \text{Lewis base}} \]