Barium Radioisotopes: Unstable isotopes of barium that decay or disintegrate emitting radiation. Ba atoms with atomic weights 126-129, 131, 133, and 139-143 are radioactive barium isotopes.Barium Sulfate: A compound used as an x-ray contrast medium that occurs in nature as the mineral barite. It is also used in various manufacturing applications and mixed into heavy concrete to serve as a radiation shield.Barium: An element of the alkaline earth group of metals. It has an atomic symbol Ba, atomic number 56, and atomic weight 138. All of its acid-soluble salts are poisonous.Radioisotopes: Isotopes that exhibit radioactivity and undergo radioactive decay. (From Grant & Hackh's Chemical Dictionary, 5th ed & McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Zinc Radioisotopes: Unstable isotopes of zinc that decay or disintegrate emitting radiation. Zn atoms with atomic weights 60-63, 65, 69, 71, and 72 are radioactive zinc isotopes.Barium Compounds: Inorganic compounds that contain barium as an integral part of the molecule.