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Barium

Barium is also the Latin name for the city Bariin Italy.
56 caesium ? barium ? lanthanum
Sr
?
Ba
?
Ra
Image:Ba-TableImage.png
periodic table
General
Name, Symbol, Number barium, Ba, 56
Chemical series alkaline earth metals
Group, Period, Block 2, 6, s
Appearance silvery white
Image:Ba,56.jpg
Atomic mass 137.327(7) g/mol
Electron configuration [Xe] 6s2
Electronsper shell 2, 8, 18, 18, 8, 2
Physical properties
Phase solid
Density(near r.t.) 3.51 g/cm³
Liquid densityat m.p. 3.338 g/cm³
Melting point 1000 K
(727 °C, 1341 °F)
Boiling point 2170 K
(1897 °C, 3447 °F)
Heat of fusion 7.12 kJ/mol
Heat of vaporization 140.3 kJ/mol
Heat capacity (25 °C) 28.07 J/(mol·K)
Vapor pressure
P/Pa 1 10 100 1 k 10 k 100 k
at T/K 911 1038 1185 1388 1686 2170
Atomic properties
Crystal structure cubic body centered
Oxidation states 2
(strongly basicoxide)
Electronegativity 0.89 (Pauling scale)
Ionization energies 1st: 502.9 kJ/mol
2nd: 965.2 kJ/mol
3rd: 3600 kJ/mol
Atomic radius 215 pm
Atomic radius (calc.) 253 pm
Covalent radius 198 pm
Miscellaneous
Magnetic ordering paramagnetic
Electrical resistivity (20 °C) 332 nΩ·m
Thermal conductivity (300 K) 18.4 W/(m·K)
Thermal expansion (25 °C) 20.6 µm/(m·K)
Speed of sound(thin rod) (20 °C) 1620 m/s
Young's modulus 13 GPa
Shear modulus 4.9 GPa
Bulk modulus 9.6 GPa
Mohs hardness 1.25
CAS registry number 7440-39-3
Notable isotopes
Main article: Isotopes of barium
iso NA half-life DM DE(MeV) DP
130Ba 0.106% Ba is stablewith 74 neutrons
132Ba 0.101% Ba is stablewith 76 neutrons
133Ba syn 10.51 y ε 0.517 133Cs
134Ba 2.417% Ba is stablewith 78 neutrons
135Ba 6.592% Ba is stablewith 79 neutrons
136Ba 7.854% Ba is stablewith 80 neutrons
137Ba 11.23% Ba is stablewith 81 neutrons
138Ba 71.7% Ba is stablewith 82 neutrons
References

Barium is a toxic chemical elementin the periodic tablethat has the symbol Ba and atomic number56. A soft silvery metallicelement, barium is an alkaline earth metaland melts at a very high temperature. Its oxide is called barytaand it is primarily found in the mineralbaritebut is never found in its pure form due to its reactivitywith air. Compounds of this metal are used in small quantities in paintsand in glassmaking.

Inhaltsverzeichnis

  • 1 Notable characteristics
  • 2 Applications
  • 3 History
  • 4 Occurrence
  • 5 Compounds
  • 6 Isotopes
  • 7 Precautions
  • 8 External links

Notable characteristics

Barium is a metallicelement that is chemically similar to calcium, yet is soft and in its pure form is silvery white resembling lead. This metal oxidizesvery easily when exposed to air and is highly reactivewith wateror 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: bariteBa(SO4) also called heavy spar.

Applications

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

  • A "getter" in vacuum tubes.
  • Barium sulfateis permanent white and is used in paint, in X-raydiagnostic work, and in glassmaking.
  • Bariteis used extensively as a weighing agent in oil welldrilling fluids and in rubberproduction.
  • Barium carbonateis a useful rat poisonand can also be used in making glass and bricks, while barium nitrateand chlorategive green colors in fireworks.
  • Impure barium sulfidephosphorescesafter exposure to the light.
  • Barium salts, especially barium sulfate, are sometimes given orally (a barium meal) or as an enema, to increase the contrast of medicalX-raysof the digestive system.
  • Lithopone, a pigmentthat contains barium sulfateand zinc sulfide, has good covering power, and does not darken in when exposed to sulfides.
  • Barium peroxidecan be used as a catalyst to start an aluminothermic reactionwhen welding rail tracks together.

History

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

Occurrence

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 mineralbaritewhich is crystalized barium sulfate. Barium is commercially produced through the electrolysisof molten barium chloride(BaCl2) Isolation (* follow):

(cathode) Ba2+* + 2e-→ Ba (anode) Cl-* → ½Cl2 (g) + e-

Compounds

The most important compounds are barium peroxide, chloride, sulfate, carbonate, nitrate, and chlorate.

See also category:Barium compounds

Isotopes

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

Precautions

All water or acid solublebarium compounds are extremely poisonous. Barium sulfatecan be used in medicine only because it does not dissolve, and is eliminated completely from the digestive tract. Unlike other heavy metalshowever, barium does not bioaccumulate. [1]

Oxidationoccurs 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.

External links

Image:Commons-logo.svg
Wikimedia Commonshas media related to:
[[Commons:{{{1|Special:Search/Barium}}}|{{{2|{{{1|Barium}}}}}}]]
  • WebElements.com – Barium



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Retrieved from "http://en.wikipedia.org/Barium"



This article is licensed under the GNU Free Documentation License.
It uses material from the http://en.wikipedia.org/wiki/Barium Wikipedia article Barium.

 
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