Choose the incorrect statement about ethylenediaminetetraacetate ion:

The correct answer is Option (4) → It is an ambidentate ligand

The ethylenediaminetetraacetate ion, EDTA⁴⁻, has six donor atoms: two nitrogen atoms and four carboxylate oxygen atoms. It binds to a metal ion through all six at the same time, so it is a hexadentate ligand, and because it binds one metal ion through several donor atoms it forms chelates. An ambidentate ligand is different: it has two different donor atoms but binds through either one of them, e.g. \( \ce{NO2^{-}} \) (through N or O) and \( \ce{SCN^{-}} \) (through S or N). So “EDTA is an ambidentate ligand” is the incorrect statement.

• Option (1) It is a hexadentate ligand — A correct statement about EDTA. EDTA⁴⁻ uses six donor atoms.

• Option (2) It forms chelate when binds with metal ion — A correct statement about EDTA. It binds one metal ion through several donor atoms at once, so it forms a chelate.

• Option (3) It can bind through two nitrogen and four oxygen atoms — A correct statement about EDTA. These are its six donor atoms.

• Option (4) It is an ambidentate ligand — The incorrect statement. EDTA is hexadentate; an ambidentate ligand binds through only one of its two different donor atoms.

NCERT (2026-27 edition):
Ligands – “… Ethylenediaminetetraacetate ion (EDTA⁴⁻) is an important hexadentate ligand. It can bind through two nitrogen and four oxygen atoms to a central metal ion. When a di- or polydentate ligand uses its two or more donor atoms simultaneously to bind a single metal ion, it is said to be a chelate ligand.”

Ligands – “… Ligand which has two different donor atoms and either of the two ligetes in the complex is called ambidentate ligand. Examples of such ligands are the NO₂⁻ and SCN⁻ ions.”