Atomic Number
56
Symbol
Ba
Atomic Weight
137.327
Discovery
Sir Humphrey Davy 1808 (England)
Electron Configuration
[Xe] 6s2
Word Origin
Greek barys, heavy or dense
Isotopes
Natural barium is a mixture of seven stable isotopes. Thirteen radioactive isotopes are known to exist.
Properties
Barium has a melting point of 725°C, a boiling point of 1640°C, and a specific gravity of 3.5 (20°C), with a valence of 2. Barium is a soft metallic element. In its pure form, it is silvery white. The metal oxidizes readily and should be stored under petroleum or other oxygen-free liquids. Barium decomposes in water or alcohol. Impure barium sulfide phosphoresces following exposure to light. All barium compounds that are soluble in water or acid are poisonous.
Uses
Barium is used as a 'getter' in vacuum tubes. Its compounds are used in pigments, paints, glassmaking, as weighting compounds, in the manufacture of rubber, in rat poison, and in pyrotechnics.
Sources
Barium is only found combined with other elements, primarily in barite or heavy spar (sulfate) and witherite (carbonate). The element is prepared by the electrolysis of its chloride.
Element Classification
Alkaline-earth Metal
Density (g/cc)
3.5
Melting Point (K)
1002
Boiling Point (K)
1910
Appearance
soft, slightly malleable, silver-white metal
Atomic Radius (pm)
222
Atomic Volume (cc/mol)
39.0
Covalent Radius (pm)
198
Ionic Radius
134 (+2e)
Specific Heat (@20°C J/g mol)
0.192
Fusion Heat (kJ/mol)
7.66
Evaporation Heat (kJ/mol)
142.0
Pauling Negativity Number
0.89
First Ionizing Energy (kJ/mol)
502.5
Oxidation States
2
Lattice Structure
Lattice Constant (Å)
5.020
References: Los Alamos National Laboratory (2001), Crescent Chemical Company (2001), Lange's Handbook of Chemistry (1952), CRC Handbook of Chemistry & Physics (18th Ed.)