Explanation:

EDTA (ethylenediaminetetraacetic acid) is a chelating agent widely used in analytical chemistry and biochemistry. It forms complexes with metal ions that are typically six-coordinate, with EDTA acting as a hexadentate ligand. This means that EDTA has six donor atoms (four carboxylate groups and two amine groups) that can bind to a metal ion.

The coordination of EDTA to a metal ion involves the formation of coordinate covalent bonds, in which the lone pair electrons on the donor atoms of EDTA are shared with the metal ion. The resulting complex is a stable, water-soluble species with a high degree of structural integrity.

EDTA is a highly effective chelating agent due to its ability to form complexes with a wide range of metal ions, including those that are highly toxic or that form insoluble salts. This property makes EDTA a valuable tool in many industrial and environmental applications, including wastewater treatment, heavy metal remediation, and metal recovery.

In summary, EDTA is a hexadentate ligand due to its ability to coordinate to a metal ion through six donor atoms. This property makes it a highly effective chelating agent with many diverse applications.