Question

Which of the following ligands is not a chelating agent?
(A) EDTA
(B) Ethylenediamine
(C) Oxalate
(D) Pyridine

Answer 1

Hint: Ligands are negatively or neutrally charged molecules capable of donating an electron pair to the metal atoms in complex compounds. Some ligands with more than two donor sites or atoms are involved in the chelate effect. The chelate effect is nothing but the formation of a cyclic structure.

Complete Step By Step Answer:
Complex compounds are also known as coordination compounds. These are the compounds that can retain their identity even dissolved in water or any other organic solvents. This is the special property of complex compounds.
Complex compounds consist of ligands and central metal atoms, in which the metal atom accepts electrons from the ligand.
When the ligand consists of two or more donor sites, then there will be a formation of two or more coordinate covalent bonds between a central metal atom and the donor atoms present in the ligand.
In the given options,
EDTA is known as ethylene diamine tetraacetate which is a hexadentate ligand.
Ethylenediamine is a bidentate ligand.
Oxalate is also a bidentate ligand.
The only pyridine is a monodentate ligand and does not involve chelation.
Thus, pyridine is not a chelating agent.
Option D is the correct one.

Note:
In oxalate, there are two oxygen atoms that can act as donor atoms. In ethylene diamine also, there were two nitrogen atoms that can act as donor atoms. There will be a new bond formation between these donor atoms and metal leads to the chelation or chelate effect.