Barium (atomic symbol: Ba, atomic number: 56) is a Block S, Group 2, Period 6 element with an atomic weight of 137.27.      The number of electrons in each of barium's shells is [2, 8, 18, 18, 8, 2] and its electron configuration is [Xe] 6s2.   The barium atom has a radius of 222 pm and a Van der Waals radius of 268 pm. Barium Bohr ModelBarium is a member of the alkaline-earth metals. 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.Elemental BariumIn its elemental form, barium is a soft, silvery-gray metal. Industrial applications for barium include acting as a "getter," or unwanted gas remover, for vacuum tubes, and as an additive to steel and cast iron.Barium is also alloyed with silicon and aluminum in load-bearing alloys.      The main commercial source of barium is the mineral barite (BaSO4);  it does not occur naturally as a free element .