(Chemical symbol: Ba). A malleable, toxic, metallic element, soft and silvery-white. Barium is used in various alloys. It belongs to the alkaline earth group, chemically resembling calcium. It occurs only in combination with other elements. Atomic number, 56; atomic weight, 137.37; melting point, 850°C (1562°F); specific gravity, 3.80 at 0°C (32°F). Salts of barium produce a green color when put in a flame.