coordinating atom:The atom having bond with the central metal ion. monodentate ligand:There is only one coordination atom in the ligand. Polydentate ligand:The ligand have two or more coordination atoms.coordinating atom：The atom having bond with the central metal ion. monodentate ligand：There is only one coordination atom in the ligand. Polydentate ligand：The ligand have two or more coordination atoms