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Barium minerals were known by alchemists in the early Middle Ages. Stones of the mineral barite found in Bologna, Italy (also known as Bologna stones ), were known to glow after exposure to light. Carl Scheele ( [link] ) identified barite in 1774, but did not isolate barium. Barium was first isolated as Ba 2+ in solution by Sir Humphry Davy ( [link] ) in 1808. The oxidized barium was at first called barote , by Guyton de Morveau, ( [link] ) which was changed by Antoine Lavoisier ( [link] ) to baryta , from which barium was derived to describe the metal.
Radium was discovered by Marie Curie ( [link] ) and her husband Pierre ( [link] ) in 1898 while studying pitchblende. After removing uranium they found that the remaining material was still radioactive. They then separated out a radioactive mixture consisting mostly of barium and an element that gave crimson spectral lines that had never been documented before. In 1910, radium was isolated as a pure metal by Curie and André-Louis Debierne ( [link] ) through the electrolysis of a radium chloride solution by using a mercury cathode and distilling in an atmosphere of hydrogen gas.
The abundance of the alkaline earth elements is given in [link] . Beryllium is rare, but found in the mineral beryl (Be 3 Al 2 Si 6 O 18 ). While magnesium is widespread within the Earth's crust, commercial sources tend to be from sea water as well as the carbonate minerals magnesite (MgCO 3 ) and dolomite [(Ca,Mg)CO 3 ]. Calcium is also commonly found as the carbonate, however, strontium and barium are present as the sulphates celestine (SrSO 4 ) and barites (BaSO 4 ), respectively.
| Element | Terrestrial abundance (ppm) |
| Be | 2.6 (Earth’s crust), 6 (soil), 2 x 10 -7 (sea water) |
| Mg | 23,000 (Earth’s crust), 10,000 (soil), 1,200 (sea water) |
| Ca | 41,000 (Earth’s crust), 20,000 (soil), 400 (sea water) |
| Sr | 370 (Earth’s crust), 200 (soil), 8 (sea water) |
| Ba | 500 (Earth’s crust), 500 (soil), 0.001 (sea water) |
| Ra | 6 x 10 -7 (Earth’s crust), 8 x 10 -7 (soil), 1 x 10 -10 (sea water) |
Calcium is a key element for living. Not only is it present as the skeletal material for shell fish and crabs (CaCO 3 ) its phosphate derivative, hydroxyapetite [Ca 5 (OH)(PO 4 ) 3 ] is the structural material of bones and teeth. Calcium is also present in soft tissue at a level of ca. 22g/kg. Calcium is a vital metal for the following:
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