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. The theory is named for Gilbert N. Lewis, who first defined it in 1923.  From p. 142:  "We are inclined to think of substances as possessing acid or basic properties, without having a particular solvent in mind.  It seems to me that with complete generality we may say that a basic substance is one which has a lone pair of electrons which may be used to complete the stable group of another atom, and that an acid substance is one which can employ a lone pair from another molecule in completing the stable group of one of its own atoms.  In other words, the basic substance furnishes a pair of electrons for a chemical bond, the acid substance accepts such a pair."

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

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 . A Brønsted-Lowry acid-base reaction occurs when the Brønsted acid is less stable than the  adduct of the base (the conjugate acid).

 References 

Category:Acids
Category:Bases