Lewis Theory
The theory defining an acid as an electron pair acceptor and a base as an electron pair donor.
Formula / equation
A + :B → A←B
Unit
Dimensionless
In depth
The most general of the three theories, it covers species with no proton at all, such as BF₃ and metal cations, and unites acid–base chemistry with coordination chemistry and much of organic mechanism. Every Brønsted acid is a Lewis acid, but not the reverse.
Examples in the real world
BF₃ accepting a lone pair from NH₃; Fe³⁺ accepting pairs from six water molecules; AlCl₃ in Friedel–Crafts reactions.