Definition of Amphoteric
The amphoteric compound is a molecule or an ion that functions as an acid as well as a base. According to Bronsted Lowry theory of acids and bases, they are such species that have the ability to either donate or accept a hydrogen ion H+ (a proton). Examples of amphoteric compounds include amino acids, proteins, etc.
Amino acids have both acid and basic groups and they exist as zwitterions at a certain pH. Some metal oxides and metal hydroxides also exhibit the phenomenon of amphoterism such as copper, zinc, aluminium, etc. It is generally dependent on the oxidation state of the metal oxides.