Brønsted–Lowry Theory
The theory defining an acid as a proton donor and a base as a proton acceptor.
Formula / equation
HA + B ⇌ A⁻ + BH⁺
Unit
Dimensionless
In depth
By focusing on proton transfer rather than on hydroxide, the theory extends to non-aqueous solvents and explains the basicity of ammonia and of anions such as carbonate. It also introduces conjugate pairs, since every proton transfer creates an acid and a base on the product side.
Examples in the real world
NH₃ + H₂O ⇌ NH₄⁺ + OH⁻, where water acts as the acid and ammonia as the base.