Question

EDTA is an example of:

• A. Unidentate Ligand
• B. Bidenatate Ligand
• C. Tridentate Ligand
• D. Hexadentate Ligand

Answer 1

The Correct Option is D

EDTA, which stands for Ethylenediaminetetraacetic acid, is a well-known ligand in coordination chemistry. To determine its denticity, let's understand its structure and binding sites.

EDTA is a complexing agent that can coordinate to a metal ion through six different donor sites. These donor atoms include four carboxylate groups (each with a negative charge that can bind to a metal ion) and two amine nitrogen atoms. This means EDTA can form a total of six coordinate bonds with a single metal ion.

Based on this, the denticity of a ligand refers to the number of donor atoms it uses to bond to a single metal ion. Thus, EDTA is correctly classified as a hexadentate ligand because it uses six donor atoms to bind.

Let's examine why the other options are incorrect:

1. Unidentate Ligand: These ligands have only one donor atom or group that can coordinate to a metal ion, such as chloride (Cl^-), water (H₂O), and ammonia (NH₃). EDTA has multiple binding sites, making this option incorrect.
2. Bidentate Ligand: Such ligands have two donor atoms. Examples include ethylenediamine (en) and oxalate ion (C₂O₄^2-). EDTA surpasses this by having six donor atoms, so this option is also incorrect.
3. Tridentate Ligand: These ligands can bind through three donor atoms. An example is diethylenetriamine. Again, EDTA has six donor sites, hence this option doesn't fit either.

Therefore, the correct answer is that EDTA is a hexadentate ligand. This makes it particularly effective at chelating metal ions, forming stable and strong complexes, which are crucial in various chemical and pharmaceutical applications.