Barium, Ba

Barium is a chemical element. It has the symbol Ba, and atomic number 56. Barium is a soft silvery metallic alkaline earth metal. It is never found in nature in its pure form due to its reactivity with air. Its oxide is historically known as baryta but it reacts with water and carbon dioxide and is not found as a mineral. The most common naturally occurring minerals are the very insoluble barium sulfate, BaSO4 (barite), and barium carbonate, BaCO3 (witherite). Benitoite is a rare gem containing barium.

Barium is a metallic element that is chemically similar to calcium but more reactive. This metal oxidizes very easily when exposed to air and is highly reactive with water or alcohol, producing hydrogen gas. Burning in air or oxygen produces not just barium oxide (BaO) but also the peroxide. Simple compounds of this heavy element are notable for their high specific gravity. This is true of the most common barium-bearing mineral, its sulfate barite BaSO4, also called 'heavy spar' due to the high density (4.5 g/cm³).

Technical Data
Symbol Be Density (20°C)/gcm-3 1.848
Atomic number 4 Melting point / °C 1287
No. of naturally occurring isotopes 1 Boiling point / °C ~2500
Atomic weight 9.01218 ΔHfus/kJmol-1 15
Electronic configuration [He] 2s2 ΔHvap/kJmol-1 309
Ionization energy/kJmol-1 899.2 Eo(M2-(aq)2e- →M(S))/V -1.85
II 1757 Electrical resistivity  
Metal radius/pm 112 (20°C)/μohm cm 4.46
Ionic radius (4-coord)/pm 27    
Evaporation Techniques
Temperature (oC) @Vap. Pressure Techniques Remarks
10-8 Torr 10-6 Torr 10-4 Torr Electron Beam Crucible Coil Boat
545 627 735 Fair Metals Tungsten Molybdenum, Tantalum & Tungsten Wets w/o alloying – reacts with ceramics.

Evaporation Materials
B1-5000-M 6.35mm & smaller pieces, packed under oil
B1-5001-M 6.35mm & smaller pieces, packed under argon
B1-5002-M 12.7mm & smaller pieces, packed under oil
B1-5003-M 12.7mm & smaller pieces, packed under argon
B1-5004-M 25mm & smaller pieces, packed under oil
B1-5005-M 1-3mm pieces, packed under argon
Rods
B1-2000-R 1" (25.4mm) packed under oil
B1-2001-R 1" (25.4mm) packed under argon