Lewis Acid and Base Theory Ivan Gradjansky and Jack Zigler

Definition Any atom/ion/molecule that donates or accepts an electron pair to form a covalent bond Suggested by G. N. Lewis, the namesake of the Lewis structure, in 1923

Lewis Acid Any atom/ion/molecule that ACCEPTS an electron pair to form a covalent bond Applies to any ‘species’ that can accept an electron pair and form a covalent bond with another Includes any compound where central atom has 3 valence electrons and 3 covalent bonds Applies in any phase

Lewis Base Any atom/ion/molecule that DONATES an electron pair to form a covalent bond Anions are Lewis acids when forming a covalent bond by donating a pair Applies in any phase Lewis Acid-Base Reaction: Formation of a covalent bond between a Lewis acid and a Lewis base

Relation to Other Definitions Broadest definition of acids and bases, and only one to not emphasize bare protons (hydrogen ions), though it can include them Often overlaps with other theories: Brønstead-Lowry bases are often Lewis bases as well

Acid Base Arrehnius H+ or H3O+ producer OH- producer Brønstead-Lowry Proton (H+) donor Proton (H+) acceptor Lewis Electron-pair acceptor Electron-pair donor

Examples H+ + NH3 → NH4+ Ag+ + 2NH3 → Ag(NH3)2 BF3 + F- → BF4- BF3 + NH3 → BF3:NH3