Barium is one of the alkali-earths metals with chemical symbol Ba and atomic number 56. It is a solid and golden-grey metal at standard pressure and temperature, it is very strong to cut, but less than Beryllium. Barium metal reacts fast with water producing Hydrogen gas and barium hydroxide. Moreover reacts with air producing a black film on its surface due to the presence of oxide, for that reason we cut the metal only once bought and put this in high quality mineral oil. Elementary Barium is hardly used except as a getter material, which binds unwanted rest gases in vacuum tubes. Barium compounds are scarcely used too, water soluble compounds of it are toxic.
The non-water-soluble barium sulfate, know as barium meal, is used as a radiographic contrast medium.