What is meant by the chelate effect? Give an example.

Chelate effect represents the stabilization of coordination compounds due to formation of metal chelates. Complexes containing chelating ligands are more stable than complexes containing unidentate ligands. Thus, $\left[Co\right(en)3{]}^{3+}$ is more stable than $\left[Co\right(N{H}_3{)}_6{]}^{3+}$. Here, en is ethylene diammine, a bidentate ligand.