Which of the following is always a bidentate ligand?

Step-by-step solution

Ammonia ( NH₃ ), water ( H₂O ), and carbon monoxide ( CO ) are monodentate ligands because they donate only one pair of electrons to the central metal atom or ion. Ethylenediamine ( H₂N-CH₂-CH₂-NH₂ ) is a bidentate ligand because it has two nitrogen atoms, each with a lone pair of electrons, which can simultaneously coordinate to the central metal atom or ion. Answer: Ethylenediamine