Britannica Sources used in this answer

What does it mean that beryllium oxide is amphoteric?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

A color-coded periodic table of the elements displays each element's symbol and atomic number, with categories such as alkali metals, noble gases, halogens, transition metals, and actinoid elements distinguished by different background colors. — alkaline-earth metal Modern version of the periodic table of the elements (printable).

To say that beryllium oxide (BeO) is amphoteric means that it possesses the chemical ability to react with both acids and bases.1

While most alkaline-earth metal oxides are basic—meaning they react with acids to form salts and water—beryllium oxide is an exception. Because it is amphoteric, it can act as a base in the presence of an acid and as an acid in the presence of a base. This property allows it to dissolve in both acidic and basic solutions.21

Historically, this behavior caused confusion; early chemists sometimes struggled to distinguish beryllia from alumina (aluminum oxide) because both substances dissolve in alkali. However, beryllium oxide is chemically distinct, and its amphoteric nature is a key characteristic that sets it apart from the more strongly basic oxides found further down the alkaline-earth group, such as magnesium oxide or calcium oxide.32