The chelate formed by the same metal ion and a chelating agent is more stable than the complex formed by the single meshed ligand with the same coordination atoms. This special stability is due to the ring formation, so this kind of The increased stability due to the formation of the chelating ring is called the chelating effect.
The stability of the chelate is measured by the stability constant of the chelate. The greater the stability constant, the higher the stability of the chelate. Assume that the chelate formed by the chelating agent and the metal ion is ML (the simplest case). Strictly speaking, the stability constant of the chelate should be expressed as:
In the formula, the activity of α-type body;
KTML: It is a constant at a certain temperature and becomes an activity constant or a thermodynamic constant.