what is a ligand in chemistry

A ligand is a molecule or ion that binds to a central metal atom or ion to form a coordination complex/Coordination_Chemistry/Structure_and_Nomenclature_of_Coordination_Compounds/Ligands). The term "ligand" comes from the Latin word "ligare," which means "to bind"/Coordination_Chemistry/Structure_and_Nomenclature_of_Coordination_Compounds/Ligands). Ligands act as Lewis bases, which means they donate electron pairs, while the central metal atom or ion acts as a Lewis acid, which means it accepts electron pairs/Coordination_Chemistry/Structure_and_Nomenclature_of_Coordination_Compounds/Ligands). Ligands can be anions, cations, or neutral molecules/Coordination_Chemistry/Structure_and_Nomenclature_of_Coordination_Compounds/Ligands). They can be characterized as monodentate, bidentate, tridentate, etc., depending on the number of donor atoms they have/Coordination_Chemistry/Structure_and_Nomenclature_of_Coordination_Compounds/Ligands). Examples of ligands include F–, Cl–, Br–, I–, S2–, CN–, NCS–, OH–, NH2–, NH3, H2O, NO, CO, NO+, and N2H5+ . The nature of bonding from metal to ligand varies from covalent bond to ionic bond. Ligands play a crucial role in coordination chemistry, dictating the reactivity of the central atom, including ligand substitution rates, the reactivity of the ligands themselves, and redox.