An amphoteric oxide is an oxide that reacts with both acids and alkalis, such as aluminium oxide; it behaves as a base towards an acid and as an acid towards an alkali.
An amphoteric oxide is an oxide that reacts with both acids and alkalis, such as aluminium oxide; it behaves as a base towards an acid and as an acid towards an alkali. Malay: oksida amfoterik · Chinese: 两性氧化物.
Most oxides fall neatly into one camp: metal oxides such as sodium oxide are basic and react only with acids, while non-metal oxides such as carbon dioxide are acidic and react only with alkalis. An amphoteric oxide sits between the two and reacts with both, which is why the word amphoteric, from a root meaning “both”, is used. In the context of Period 3, this dual behaviour appears where the character of the element is changing from metal to non-metal, so it is closely tied to an element’s position in the table.
Example. Aluminium oxide, Al₂O₃, is the standard example. It reacts with an acid like a base, dissolving in dilute hydrochloric acid to form a salt and water, and it also reacts with a hot concentrated alkali like an acid. Because it does both, it is classed as amphoteric rather than simply basic or acidic. Zinc oxide behaves in the same amphoteric way.
Confusion to avoid. Do not label every metal oxide amphoteric, most are simply basic. Amphoteric is the special “both” case, seen in a few oxides such as those of aluminium and zinc, and it is different from a neutral oxide, which reacts with neither acids nor alkalis.
In the Periodic Table of Elements chapter the amphoteric oxide marks the changeover from metal to non-metal across Period 3, so recognising it helps you read how properties shift along a period.
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