Question

A chelating agent possesses :

• A. two or more electron pair for co-ordination
• B. polydentate nature
• C. formation of strain free ring with central atom
• D. monodentate nature

Answer 1

Answer: (A), (B), (C)

The correct options are
A two or more electron pair for co-ordination
B polydentate nature
C formation of strain free ring with central atom

Chelation

Polydentate ligands whose structures permit the attachment of their two or more donor atoms (or sites) to the same metal ion simultaneously and thus produce one or one rings are called chelating ligands (from the Greek for claw) or chelating groups.

However, it should be noted that every multidentate ligand is not necessarily a chelating ligand - the coordinating atoms of the ligand may be so arranged that they cannot be coordinated to the same metal atom to produce a ring structure. Thus $\ddot{N}{H}_2-C{H}_2-C{H}_2-\ddot{N}{H}_2$ is a chelating ligand, while

Ref. image is not, although both are diamines. The formation of such rings is termed chelation and the resulting ring structures have been called chelate rings or simply chelates by morgan and Drew. These are also called chelated complexes or cyclic complexes and the term chelation is also called cyclisation.