The oxides of the Group I and Group II elements react with water to form strongly basic solutions contains hydroxide anion, OH–.
Metals react with oxygen to give basic compounds of oxygen. These compounds are usually ionic in nature. Group 1, 2 and lanthanides form basic compounds of oxygen when they react with dioxygen. During the formation of these compounds, a large amount of energy is released. These compounds readily react with water except a few exceptions.
Examples: M2O3, MO2, ThO2