The defining characteristic of the Brønsted-Lowry definition of acids and bases is the transfer of protons (H+). Here's the breakdown:

* Acids: Brønsted-Lowry acids are proton donors. They donate a proton (H+) to another molecule or ion.

* Bases: Brønsted-Lowry bases are proton acceptors. They accept a proton (H+) from another molecule or ion.

Example:

In the reaction of hydrochloric acid (HCl) with water (H2O):

* HCl (acid) + H2O (base) → H3O+ (conjugate acid) + Cl- (conjugate base)

* HCl donates a proton (H+) to form H3O+ (hydronium ion), making it an acid.

* H2O accepts a proton (H+) to form H3O+, making it a base.

Key Points:

* The Brønsted-Lowry definition focuses on the movement of protons during chemical reactions.

* This definition expands upon the Arrhenius definition, which only defines acids and bases in aqueous solutions.

* The concept of conjugate acids and bases is essential in the Brønsted-Lowry theory.