Aluminium oxide (Al2O:) shows basic as well as acidic behaviour because it reacts with both acids and bases. Thus, it is considered an amphoteric oxide. The two types of reactions given by AI2O3 are as follows:

In this reaction, Al2O3 behaves as a basic oxide because it reacts with an acid to form salt and water.

In this reaction, Al2O3 behaves as an acidic oxide because it reacts with a base to form salt and water.