What is meant by unidentate, didentate and ambidentate ligands? Give two examples for each.
Unidentate ligands are ligands that bind to a metal ion through a single donor atom. Examples: Cl⁻, H₂O, NH₃.
Didentate ligands are ligands that can bind through two donor atoms simultaneously to a single metal ion. Examples: H₂NCH₂CH₂NH₂ (ethane-1,2-diamine), C₂O₄²⁻ (oxalate).
Ambidentate ligands are ligands which have two different donor atoms and can coordinate through either of the two donor atoms to the central metal ion. Examples: NO₂⁻ (can coordinate through nitrogen or oxygen), SCN⁻ (can coordinate through sulphur or nitrogen).
Explanation
The answer defines all three types of ligands as per NCERT textbook. Unidentate ligands have single donor atom (denticity=1), didentate have two donor atoms (denticity=2), and ambidentate ligands have two different donor atoms but can use only one at a time. The examples are directly taken from the context provided.