<Tr> <Td> </Td> <Td> This section needs expansion . You can help by adding to it . (November 2012) </Td> </Tr> <P> Of the six alkaline earth metals, beryllium, calcium, barium, and radium have at least one naturally occurring radioisotope; magnesium and strontium do not . Beryllium - 7, beryllium - 10, and calcium - 41 are trace radioisotopes; calcium - 48 and barium - 130 have very long half - lives and thus occur naturally on earth; and all isotopes of radium are radioactive . Calcium - 48 is the lightest nuclide to undergo double beta decay . Calcium and barium are weakly radioactive: calcium contains about 0.1874% cacium - 41, and barium contains about 0.1062% barium - 130 . </P> <P> The alkaline earth metals are named after their oxides, the alkaline earths, whose old - fashioned names were beryllia, magnesia, lime, strontia, and baryta . These oxides are basic (alkaline) when combined with water . "Earth" is an old term applied by early chemists to nonmetallic substances that are insoluble in water and resistant to heating--properties shared by these oxides . The realization that these earths were not elements but compounds is attributed to the chemist Antoine Lavoisier . In his Traité Élémentaire de Chimie (Elements of Chemistry) of 1789 he called them salt - forming earth elements . Later, he suggested that the alkaline earths might be metal oxides, but admitted that this was mere conjecture . In 1808, acting on Lavoisier's idea, Humphry Davy became the first to obtain samples of the metals by electrolysis of their molten earths, thus supporting Lavoisier's hypothesis and causing the group to be named the alkaline earth metals . </P> <P> The calcium compounds calcite and lime have been known and used since prehistoric times . The same is true for the beryllium compounds beryl and emerald . The other compounds of the alkaline earth metals were discovered starting in the early 15th century . The magnesium compound magnesium sulfate was first discovered in 1618 by a farmer at Epsom in England . Strontium carbonate was discovered in minerals in the Scottish village of Strontian in 1790 . The last element is the least abundant: radioactive radium, which was extracted from uraninite in 1898 . </P>

Why group 2 elements called alkaline earth metals