Question

Which of the following is a chelating ligand?

• A. ( NH_3 \)
• B. ( H_2 O \)
• C. ( Cl- \)
• D. ( C_2 O_42- \)

Hint:

Chelation generally increases the stability of a complex. Look for molecules with multiple lone pairs on different atoms that are positioned to "grab" a metal like a claw.

Answer 1

The Correct Option is D

Concept: A chelating ligand is a polydentate ligand that can bond to a single central metal atom through two or more donor atoms simultaneously, forming a ring structure (chelate ring). 

Step 1: Identify the denticity of the options.
\( NH_3 \) (Ammonia): Unidentate (one donor N atom). \( H_2 O \) (Water): Unidentate (one donor O atom). \( Cl- \) (Chloride): Unidentate (one donor Cl atom). \( C_2 O_42- \) (Oxalate): Didentate (two donor O atoms).
 
Step 2: Determine the chelating agent.
Because the oxalate ion (\( C_2 O_42- \)) has two donor atoms that can coordinate to the same metal ion to form a five-membered ring, it is classified as a chelating ligand.