Ligand Is an ion or molecule, which donates a pair of electrons to the central metal atom or ion to form a coordination complex.
Ligands can be anions, cations and neutral molecules.
Ligands act as a Lewis base and central metal atoms are viewed as Lewis acid.
Ligands can be classified as monodentate, bidentate, tridentate and polydentate ligands depending upon the number of ligand donor atoms that attach to the metal atom or ion.