The coordination number of a central metal atom in a complex is determined by :
(1) the number of only anionic ligands bonded to the metal ion
(2) the number of monodentate ligands around a metal ion bonded by pi-bonds
(3) the number of monodentate ligands around a metal ion bonded by σ and pi-bonds both
(4) the number of monodentate ligands around a metal ion bonded by σ -bonds