In the Lewis theory, how is a base defined?

In Lewis theory, a base is defined as an electron pair donor. This definition is rooted in the concept that bases provide a pair of electrons to form a bond, thus facilitating the reaction with an acid, which is defined as an electron pair acceptor. The interaction between an acid and a base in Lewis theory emphasizes the transfer of electron pairs rather than the transfer of protons, which is the basis for Brønsted-Lowry acid-base theory.

When a Lewis base donates an electron pair, it can form coordinate covalent bonds with a substance that can accept these electrons, demonstrating its role in chemical reactions. This broader definition allows for a wider range of substances to act as bases beyond those that merely accept protons, thus encompassing various reactions in organic and inorganic chemistry.