Name, Symbol, Number Barium, Ba, 56
Series alkaline earth metals
Group, Period, Block 2(IIA), 6, s
Density, Hardness 3510 kg/m3, 1.25
Appearance silvery white
Atomic Properties
Atomic weight 137.327 amu
Atomic radius (Calc.) 215 pm (253 pm)
Covalent radius 198 pm
van der Waals radius no information
Electron configuration [Xe]6s2
e- 's per energy level 2, 8, 18, 18, 8, 2
Oxidation states (Oxide) 2 (strong base)
Crystal structure Cubic body centered
Physical Properties
State of matter solid (paramagnetic)
Melting point 1000 K (727.2 ?C / 1341 ?F)
Boiling point 2143 K (1870 ?C / 3398 ?F)
Molar volume 38.16 ×10-6 m3/mol
Heat of vaporization 142 kJ/mol
Heat of fusion 7.75 kJ/mol
Vapor pressure 98 Pa at 371 K
Speed of sound 1620 m/s
Electronegativity 0.89(Pauling scale)
Specific heat capacity 204 J/(kg*K)
Electrical conductivity 3 106/m ohm
Thermal conductivity 18.4 W/(m*K)
1st ionization potential 502.9 kJ/mol
2nd ionization potential 965.2 kJ/mol
3rd ionization potential 3600 kJ/mol
Most Stable Isotopes
iso NA half-life DM DE MeV DP
130Ba 0.106% Ba is stable with 74 neutrons
132Ba 0.101% Ba is stable with 76 neutrons
133Ba {syn.} 10.51 y epsilon 0.517 133Cs
134Ba 2.417% Ba is stable with 78 neutrons
135Ba 6.592% Ba is stable with 79 neutrons
136Ba 7.854% Ba is stable with 80 neutrons
137Ba 11.23% Ba is stable with 81 neutrons
138Ba 71.7% Ba is stable with 82 neutrons
SI units & STP are used except where noted.

Barium is a toxic chemical element in the periodic table that has the symbol Ba and atomic number 56. A soft silvery metallic element, barium is an alkaline earth metal and melts at a very high temperature. Its oxide is called baryta and it is primarily found in the mineral barite but is never found in its pure form due to its reactivity with air. Compounds of this metal are used in small quantities in paints and in glassmaking.

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Notable characteristics

Barium is a metallic element that is chemically similar to calcium, yet is soft and in its pure form is silvery white resembling lead. This metal oxidizes very easily and when exposed to air and is highly reactive with water or alcohol. Barium is decomposed by water or alcohol. Some of the compounds of this element are remarkable for their high specific gravity, as is its sulfate: barite Ba(SO4) also called heavy spar.


Barium is primarily used in sparkplugs, vacuum tubes, fireworks, and in fluorescent lamps. Also:


Barium (Greek "barys" meaning "heavy") was first identified in 1774 by Carl Scheele and extracted in 1808 by Sir Humphry Davy in England. The oxide was at first called barote, by Guyton de Morveau, which was changed by Antoine Lavoisier to baryta, which soon was modified to "barium" to describe the metal.


Because barium quickly becomes oxidized in air, it is difficult to obtain this metal in its pure form. It is primarily found in and extracted from the mineral barite which is crystalized barium sulfate. Barium is commercially produced through the electrolysis of molten barium chloride (BaCl2) Isolation (* follow):

(cathode) Ba2+* + 2e- → Ba (anode) Cl-* → ?Cl2 (g) + e-


The most important compounds are barium peroxide, chloride, sulfate, carbonate, nitrate, and chlorate. When burned, barium salts glows green.


Naturally occurring barium is a mix of seven stable isotopes. There are twenty-two isotopes known, but most of these are highly radioactive and have half-lifes in the several millisecond to several minute range. The only notable exception is barium-133 which has a half-life of 10.51 years.


All water or acid soluble barium compounds are extremely poisonous. Oxidation occurs very easily and, to remain pure, barium should be kept under a petroleum-based fluid (such as kerosene) or other suitable oxygen-free liquids that exclude air. Barium sulfate can be used in medicine only because it does not dissolve, and is eliminated completely from the digestive tract.

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