Amphoteric: definition in chemistry
Amphoteric: Able to react as both an acid and a base. Aluminum oxide, zinc oxide and water are examples.
An amphoteric oxide or hydroxide dissolves in acids, where it acts as a base, and also in strong bases, where it acts as an acid. For example, aluminum hydroxide reacts with hydrochloric acid to form aluminum chloride and with sodium hydroxide to form sodium aluminate. Water is amphoteric because it can both donate and accept a hydrogen ion (H⁺).
Examples
- Aluminum oxide (Al₂O₃) reacts with both acids and bases
- Zinc oxide (ZnO) dissolves in hydrochloric acid and in sodium hydroxide
- Water (H₂O) can donate or accept a hydrogen ion
- The bicarbonate ion (HCO₃⁻) can neutralize both acids and bases
On the periodic table
Across a period, oxides change from basic on the left to acidic on the right, and many amphoteric oxides come from metals in between, such as beryllium, aluminum, zinc, tin and lead.