Barium - Ba
Discovered in 1808 by Sir Humphrey Davy in London, England. Elemental barium does not occur naturally although it has an abundance within the earth's crust of 500 ppm. It is obtained by heating BaO with Al and, once refined, barium is a silvery white, soft metal which oxidises readily in air and water. Barium compounds, particularly BaSO₄, are used for various applications, including the manufacture of paint, as an addition to heavy duty drilling oils and in radiology as "barium meal" where it is used to outline a patient's alimentary tract, the X-rays being stopped by the barium sulphate.