# What is an acid?

May 15, 2016

See below.

#### Explanation:

There are three definitions of acids that could be found in literature that have been given by four scientists (2 scientists gave the same definition, Brønsted and Lowry):

Arrhenius definition:
Acids: produce hydrogen ions (${H}^{+}$) in aqueous solution. Arrhenius acids include compounds such as $H C l$, $H C N$, and ${H}_{2} S {O}_{4}$ that ionize in water to give the ${H}^{+}$ ion.

Brønsted-Lowry definition:
Acids: compounds that are proton (${H}^{+}$) donors.
This is similar to the Arrhenius definition but it is more general and it is not limited to aqueous solution only.

Lewis definition:
Acids: compounds that are an electron pair acceptors.

Acids & Bases | Nature, Strength & pH Scale.