November 2, 2011, 4:00 pm

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Physical Properties
Color silvery-white
Phase at Room Temp. solid
Density (g/cm3) 3.62
Hardness (Mohs) ---
Melting Point (K) 998.2
Boiling Point (K) 2123
Heat of Fusion (kJ/mol) 7.657
Heat of Vaporization (kJ/mol) 151
Heat of Atomization (kJ/mol) 180
Thermal Conductivity (J/m sec K) 18.4
Electrical Conductivity (1/mohm cm) ---
Source Barite (sulfate)
Atomic Properties
Electron Configuration [Xe]6s2
Number of Isotopes 48 (7 natural)
Electron Affinity (kJ/mol) ---
First Ionization Energy (kJ/mol) 502.9
Second Ionization Energy (kJ/mol) 965.2
Third Ionization Energy (kJ/mol) ---
Electronegativity 0.89
Polarizability (Å3) 39.7
Atomic Weight 137.33
Atomic Volume (cm3/mol) 37.9
Ionic Radius2- (pm) ---
Ionic Radius1- (pm) ---
Atomic Radius (pm) 222
Ionic Radius1+ (pm) ---
Ionic Radius2+ (pm) 149
Ionic Radius3+ (pm) ---
Common Oxidation Numbers +2
Other Oxid. Numbers ---
In Earth's Crust (mg/kg) 4.25×102
In Earth's Ocean (mg/L) 1.3×10-2
In Human Body (%) 0.00003%
Regulatory / Health
CAS Number 7440-39-3
OSHA Permissible Exposure Limit  No limit
OSHA PEL Vacated 1989 No limit
NIOSH Recommended Exposure Limit  No limit
Mineral Information Institute
Jefferson Accelerator Laboratory

Barium is a the chemical element with atomic number 56. Barium, with the periodic table symbol Ba, is the fifth element in Group 2; this element presents as a soft silvery metallic alkaline earth metal. Barium does not occur naturally in a pure form due to its very high chemical reactivity with the atmosphere. Its oxide is termed Barium hydroxide, although this molecule reacts with water and carbon dioxide and does not occur as a mineral in the Earth's crust or atmosphere.

This article is written at a definitional level only. Authors wishing to improve this entry are inivited to expand the present treatment, which additions will be peer reviewed prior to publication of any expansion.


(2011). Barium. Retrieved from


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