Barium

Barium is also the Latin name for the city Bari in Italy.

56 caesium ← barium → lanthanum Sr ↑ Ba ↓ Ra periodic table
General
Name, Symbol, Number	barium, Ba, 56
Chemical series	alkaline earth metals
Group, Period, Block	2, 6, s
Appearance	silvery white
Atomic mass	137.327(7) g/mol
Electron configuration	[Xe] 6s2
Electrons per shell	2, 8, 18, 18, 8, 2
Physical properties
Phase	solid
Density (near r.t.)	3.51 g/cm³
Liquid density at 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 basic oxide)
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 stable with 74 neutrons 132Ba 0.101% Ba is stable with 76 neutrons 133Ba syn 10.51 y ε 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
References

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.

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 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.

Applications

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

• A "getter" in vacuum tubes.
• Barium sulfate is permanent white and is used in paint, in X-ray diagnostic work, and in glassmaking.
• Barite is used extensively as a weighing agent in oil well drilling fluids and in rubber production.
• Barium carbonate is a useful rat poison and can also be used in making glass and bricks, while barium nitrate and chlorate give green colors in fireworks.
• Impure barium sulfide phosphoresces after 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 medical X-rays of the digestive system.
• Lithopone, a pigment that contains barium sulfate and zinc sulfide, has good covering power, and does not darken in when exposed to sulfides.
• Barium peroxide can be used as a catalyst to start an aluminothermic reaction when welding rail tracks together.

History

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.

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 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^-* → 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 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.

Precautions

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.

External links

Wikimedia Commons has media related to:

Barium

• WebElements.com – Barium