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 The number of such ligating groups is called the
denticity of the ligand Such complexes, called chelate complexes
tend to be more stable than similar complexes containing unidentate
ligands Ligand which has two different donor atoms and either of
the two ligetes in the complex is called ambidentate
ligand