Each of the alkaline earth metals reacts with HCl, also known as hydrochloric acid, to form hydrogen gas and its corresponding metal chloride solution. The reaction becomes stronger the further down the group the element is on the periodic table.
Beryllium has the weakest reaction with hydrochloric acid, while radon reacts the most vigorously. The other members of the group, in order from the weakest reaction to the strongest, are magnesium, calcium, strontium and barium. Although they are active, each of the alkali earth metals is less reactive than its neighboring alkali metal. Still, most of the alkali earth metals chemical behavior can be predicted by its neighboring alkali metal.
The alkali earth metals are all soft, silver colored metals that appear in various quantities in nature. The term alkali comes from the fact that the oxides of these elements form alkaline or basic solutions when put into water. Early chemists originally classified the oxides of these elements, which quickly form when these substances are exposed to air, as they had yet to isolate them in their pure form. This early classification of the oxides is also where the term earth comes from, as this was a term that was applied to any non-metallic substance that could not be dissolved in water.