On metal ions and ligands. Because the formation of complexes is mainly between positively charged metal ions and ligand anions or dipole molecules, the greater the ionic potential of metal ions (the ratio of cationic charge to its radius), the more stable the complexes with the same ligands are. The stability of the complex is also related to the polarizability of the ligand anion. In a certain range, the greater the polarization of anions, the easier it is for ligands to become electron donors. For example, for divalent metal ions from Mn to Zn in the fourth cycle, the stability of their complexes is based on F.

Chelation will also affect the stability of complexes, that is, ligands with more than two teeth are linked to metal ions in more than one position to form rings. The stability of general complexes increases with the increase of chelating degree, for example, the stability of ethylenediamine complexes is greater than that of ammonia complexes.