Abstract: It has been over four hundred years since the proposal of acid-base theory in the 17th century. The understanding and exploration of acids and bases have been an extensive process. Initially, chemists sought to define acids, bases, and acid-base reactions. So far, several theories have been proposed, including the acid-base ionization theory, acid-base solvent theory, Brønsted-Lowry acid-base theory, Lewis acid-base theory, and the soft and hard acid-base theory. These theories are interrelated and complementary, deepening the understanding of the nature of acids and bases and fostering the development of chemistry.

Key words: Lewis acid-base theory, Acid-base ionization, Hindered acid-base pair