Lewis acid-base theory

In chemistry, the Lewis acid-base theory is a specific group of definitions that say what an acid and base are. It is one of the two main definitions used in modern chemistry. The other is the Brønsted–Lowry acid–base theory.^[1] The theory is named for Gilbert N. Lewis, who first defined it in 1923.^[2]

Definition

Lewis's definition says a base is any substance which has a lone pair of electrons,^[3] and an acid is any substance which has empty space to receive a pair of electrons.^[4]

Unlike other acid-base theories, Lewis acid-base reactions are addition reactions that form a single combined molecule, a Lewis adduct. In Lewis theory, Brønsted acids are adducts of their conjugate base and the Lewis acid H⁺. A Brønsted-Lowry acid-base reaction occurs when the Brønsted acid is less stable than the H⁺ adduct of the base (the conjugate acid).