The dissolving of BeO is an example of the usefulness of acids and
bases in promoting reactions that do not proceed easily or at all
in neutral water solution.
Because BeO is insoluble in pure water but reacts with either an
acid (like a base would) or a base (like an acid would), we say
that it is amphoteric, from a Greek word meaning "both
BeO is on the borderline between bases and acids, and the explanation
for its amphoteric behavior is to be found in the greater electronegativity
of Be than Li, and the partial covalent character of the Be-O bond.
Other, heavier metals, such as aluminum, which also are on the borderline
between metallic and nonmetallic behavior, have amphoteric oxides,
with both basic and acidic properties.