Barium Barium Barium is a chemical element with symbol Ba and atomic number 56. It is the fifth element in group 2 and is a soft, silvery alkaline earth metal. Because of its high chemical reactivity, barium is never found in nature as a free element. Its hydroxide, known in pre-modern times as baryta, does not occur as a mineral, but can be prepared by heating barium carbonate. The most common naturally occurring minerals of barium are barite (now called baryte) (barium sulfate, BaSO) and witherite (barium carbonate, BaCO), both insoluble in water. The name "barium" originates from the alchemical derivative
Chemical element neutrons) for a particular isotope of an element, with this number combined with the pertinent element's symbol. IUPAC prefers that isotope symbols be written in superscript notation when practical, for example C and U. However, other notations, such as carbon-12 and uranium-235, or C-12 and U-235, are also used. As a special case, the three naturally occurring isotopes of the element hydrogen are often specified as H for H (protium), D for H (deuterium), and T for H (tritium). This convention is easier to use in chemical equations, replacing the need to write out the mass number for each atom.