Question

Ethylene diaminetetraacetate (EDTA) ion is

• A. Tridentate ligand with three “N” donor atoms
• B. Hexadentate ligand with four “O” and two “N” donor atoms
• C. Unidentate ligand
• D. Bidentate ligand with two “N” donor atoms

Answer 1

The Correct Option is B

To determine the characteristics of the Ethylene diaminetetraacetate (EDTA) ion, we first need to understand its chemical structure and properties:

EDTA:

• EDTA stands for Ethylene diaminetetraacetic acid. When it loses hydrogen ions, it becomes the EDTA ion.
• The EDTA ion is a complexing agent that can form multiple bonds with a metal ion.
• Its structure consists of two amine groups (\( -NH_2 \)) and four carboxylate groups (\( -COO^- \)).
• The two nitrogen (\( N \)) atoms and four oxygen (\( O \)) atoms can donate electron pairs to a central metal ion, allowing EDTA to function as a ligand.

Concept of Denticity:

• The term "denticity" refers to the number of donor atoms on a ligand that bind to a central metal ion.
• In this case, EDTA is a hexadentate ligand because it uses six donor atoms (four oxygen atoms and two nitrogen atoms) to form coordinate bonds with a metal ion.

Answer Analysis:

• Tridentate ligand with three “N” donor atoms: Incorrect. EDTA does not have three nitrogen donor atoms; it has two.
• Hexadentate ligand with four “O” and two “N” donor atoms: Correct. This matches the description of the EDTA ligand, which can donate from four oxygen and two nitrogen atoms.
• Unidentate ligand: Incorrect. A unidentate ligand has only one donor atom.
• Bidentate ligand with two “N” donor atoms: Incorrect. EDTA is not bidentate as it uses six donor atoms in total, not just two.

Thus, given these explanations and analyses, the correct answer is that EDTA is a hexadentate ligand with four “O” and two “N” donor atoms.