Ligand

A ligand is a molecule or ion that binds to a central metal atom to form a coordination complex. Ligands can be either simple ions, such as chloride (Cl⁻) or hydroxide (OH⁻), or larger molecules such as ammonia (NH₃) or ethylenediamine. They typically have one or more pairs of electrons that can be donated to the metal atom, forming coordinate covalent bonds.