In
the Br?Nsted definition, an acid is a chemical species
that can donate a proton to another species
(a base). In the Lewis definition, an acid is a chemical species that can accept (and share) a pair of electrons from another species.
Hydrochloric acid is a Br?Nsted acid; the proton it donates is a Lewis acid.
A neutral Lewis acid and a neutral Lewis base can
commonly form a dipolar bond.
