Describe an acid or base in terms of its relationship to protons

Acids are donors of protons (H+) and bases are acceptors of protons.

For example:

1) hydrochloric acid (HCl) in reaction with water give one proton to water and become chloride anion (Cl-).

2) ammonia (NH3) Is base, in reaction with water accepts one protone and become ammonium cation (NH4+).