56
  Ba  
137.327000
Barium

Name: Barium
Symbol: Ba
Atomic Number: 56
Atomic Weight: 137.327000
Family:  Alkaline Earth Metals
CAS RN: 7440-39-3
Description: A silvery white, soft metallic element.
State (25C): Solid
Oxidation states: +2

Molar Volume: 38.21 cm3/mole
Valence Electrons: 6s2

Boiling Point:  2171K, 1898C, 3448F
Melting Point:
1002K, 729C, 1344F
Electrons Energy Level: 2, 8, 18, 18, 8, 2
Isotopes: 33 + 7 Stable
Heat of Vaporization: 142 kJ/mol
Heat of Fusion: 7.75 kJ/mol
Density: 3.59 g/cm3 @ 300K
Specific Heat: 0.204 J/gK
Atomic Radius: 2.78
Ionic Radius: 1.35
Electronegativity: 0.89 (Pauling); 0.97 (Allrod Rochow)
Vapor Pressure: 98 Pa @ 729C
4
Be
9.012
Barium (Greek "barys" meaning "heavy") was first identified in 1774 by Carl Scheele.   It was first isolated by Sir Humphry Davy, an English chemist, in 1808 through the electrolysis of molten baryta (BaO).  The oxide was at first called Barote, by Guyton de Morveau, which was changed by Antoine Lavoisier to Baryta, from which "Barium" was derived to describe the metal.

Barium is never found free in nature since it reacts with oxygen in the air, forming barium oxide (BaO), and with water, forming barium hydroxide (Ba(OH)2) and hydrogen gas (H2).   Barium is most commonly found as the mineral barite (BaSO4) and witherite (BaCO3) and is primarily produced through the electrolysis of barium chloride (BaCl2).

Barium sulfate (BaSO4), a common barium compound, is used as a filler for rubber, plastics and resins. It can be combined with zinc oxide (ZnO) to make a white pigment known as lithophone or with sodium sulfate (Na2SO4) to make another white pigment known as blanc fixe. Stones made from impure barium sulfate glow when exposed to light and will glow in the dark for up to six years if intensely heated in the presence of charcoal. These stones, known as Bologna stones, were discovered near Bologna, Italy in the early 1500s and were thought to possess magical properties by alchemists.

12
Mg
24.30
20
Ca
40.07
38
Sr
87.62
56
Ba
137.3
88
Ra
226.0

1s2 2s2p6 3s2p6d10 4s2p6d10 5s2p6 6s2

Characteristics

80px-Flammable.jpg (2186 bytes) Barium is a metallic element that is chemically similar to Calcium but more reactive.  This metal oxidizes very easily when exposed to air and is highly reactive with water or alcohol, producing Hydrogen Gas, H2.  Burning in air or Oxygen produces not just Barium Oxide (BaO) but also the Peroxide.

  Simple compounds of this heavy element are notable for their high specific gravity.  This is true of the most common Barium-bearing mineral, its Sulfate Barite, BaSO4, also called 'heavy spar' due to the high density (4.5 g/cm).

1s2
2s2 2p6
3s2 3p6 3d10
4s2 4p6 4d10
5s2 5p6
6s2

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, BaCl):

(Cathode) Ba2+ + 2e- rarrow.gif (63 bytes) Ba (Anode) Cl- rarrow.gif (63 bytes) Cl2 (g) + e-

Applications

Barium has some medical and many industrial uses:

Compounds

The most important compounds are:

Barium Peroxide, BaO2 Barium Chloride, BaCl2
Barite, Barium Sulfate, BaSO4 Witherite, Barium Carbonate, BaClO3
Barium Nitrate, BaNO3 Barium Chlorate, BaClO3
Barium Titanate, BaTiO3 Barium Ferrite, BaO6Fe2O3

Isotopes

Naturally occurring Barium is a mix of seven stable isotopesThere are thirty-three isotopes known, but most of these are highly radioactive and have half-lifes in the several millisecond to several minute range.  The only notable exceptions are 133Ba which has a half-life of 10.51 years, and 137mBa (2.55 minutes).

atom.gif (700 bytes)

Isotope Atomic Mass Half-Life
Ba114 113.951 0.43 seconds
Ba115 114.948 0.4 seconds
Ba116 115.942 0.3 seconds
Ba117 116.939 1.75 seconds
Ba118 117.933 5.5 seconds
Ba119 118.93 5.4 seconds
Ba120 119.926 32 seconds
Ba121 120.924 29.7 seconds
Ba122 121.92 1.95 minutes
Ba123 122.919 2.7 minutes
Ba124 123.9151 11 minutes
Ba125 124.915 3.5 minutes
Ba126 125.9112 100 minutes
Ba127 126.911 12.7 minutes
Ba128 127.9083 2.43 days
Ba129 128.9087 2.23 hours
Ba130 129.9063 Stable
Ba131 130.9069 11.50 days
Ba132 131.9051 Stable
Ba133 132.906 10.51 years
Ba134 133.9045 Stable
Ba135 134.9057 Stable
Ba136 135.9046 Stable
Ba137 137.9058 Stable
Ba137m 137.9058 2.55 minutes
Ba138 137.9052 Stable
Ba139 138.9088 83.06 minutes
Ba140 139.9106 12.752 days
Ba141 140.9144 18.27 minutes
Ba142 141.9165 10.6 minutes
Ba143 142.9206 14.33 seconds
Ba144 143.9229 11.5 seconds
Ba145 144.9269 4.31 seconds
Ba146 145.9301 2.22 seconds
Ba147 146.934 0.893 seconds
Ba148 147.938 0.607 seconds
Ba149 148.942 0.344 seconds
Ba150 149.946 0.3 seconds
Ba151 150.951 > 150 ms
Ba152 151.954 ˜ 0.1 seconds
Ba153 152.96 ˜ 0.08 seconds

Precautions

40px-Skull_and_crossbones.svg.jpg (1420 bytes) All water or acid soluble Barium compounds are extremely poisonous.   At low doses, Barium acts as a muscle stimulant, while higher doses affect the nervous system, causing cardiac irregularities, tremors, weakness, anxiety, dyspnea and paralysis.

This may be due to its ability to block Potassium Ion channels which are critical to the proper function of the nervous system.

Barium Sulfate can be used in medicine only because it does not dissolve, and is eliminated completely from the digestive tract. Unlike other heavy metals, Barium does not bioaccumulate.  However, inhaled Barium dust can accumulate in the lungs, a benign condition called baritosis.

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.


atom.gif (700 bytes)

Barium Data

 

Atomic Structure

Atomic Radius (): 2.78
Atomic Volume cm3/mol : 39.24cm3/mol
Covalent Radius: 1.98
Crystal Structure: Cubic body centered
Ionic Radius: 1.35

Chemical Properties

Electrochemical Equivalents: 2.5621 g/amp-hr
Electron Work Function: 2.7eV
Electronegativity: 0.89 (Pauling); 0.97 (Allrod Rochow)
Heat of Fusion: 7.75 kJ/mol
Incompatibilities: unknown
First Ionization Potential: 5.212
Second Ionization Potential: 10.004
Third Ionization Potential: unknown
Valence Electron Potential(-eV): 21.3
Ionization Energy (eV): 5.212 eV

Physical Properties

Atomic Mass Average: 137.327
Boiling Point: 2171K, 1898C, 3448F
Melting Point: 1002K, 729C, 1344F
Heat of Vaporization: 142 kJ/mol
Coefficient of Lineal Thermal Expansion/K-1: 18.1E-6
Electrical Conductivity: 0.03 106/cm
Thermal Conductivity: 0.184 W/cmK
Density: 3.59 g/cm3 @ 300K
Elastic Modulus (Bulk): 9.6/GPa
Elastic Modulus (Rigidity): 4.86/GPa
Elastic Modulus Youngs: 12.8/GPa
Enthalpy of Atomization: 175.7 kJ/mole @ 25C
Enthalpy of Fusion: 7.66 kJ/mole
Enthalpy of Vaporization: 140 kJ/mole
Hardness Scale (Brinell): unknown
Hardness Scale (Mohs): 1.25
Hardness Scale (Vickers): unknown
Flammability Class: unknown
Molar Volume: 38.21 cm3/mole
Optical Reflectivity: unknown
Optical Refractive Index: unknown
Relative Gas Density (Air=1): unknown
Specific Heat: 0.204 J/gK
Vapor Pressure: 98 Pa @ 729C
Estimated Crustal Abundance: 4.25102 milligrams per kilogram
Estimated Oceanic Abundance:
1.310-2 milligrams per liter


(Gr. barys, heavy) Baryta was distinguished from lime by Scheele in 1774; the element was discovered by Sir Humphrey Davy in 1808. It is found only in combination with other elements, chiefly with sulfate and carbonate and is prepared by electrolysis of the chloride. Barium is a metallic element, soft, and when pure is silvery white like lead; it belongs to the alkaline earth group, resembling calcium chemically. The metal oxidizes very easily and should be kept under petroleum or other suitable oxygen-free liquids to exclude air. It is decomposed by water or alcohol. The metal is used as a "getter" in vacuum tubes. The most important compounds are the peroxide, chloride, sulfate, carbonate, nitrate, and chlorate. Lithopone, a pigment containing barium sulfate and zinc sulfide, has good covering power, and does not darken in the presence of sulfides. The sulfate, as permanent white is also used in paint, in X-ray diagnostic work, and in glassmaking. Barite is extensively used as a weighing agent in oilwell drilling fluids, and is used in making rubber. The carbonate has been used as a rat poison, while the nitrate and chlorate give colors in pyrotechny. The impure sulfide phosphoresces after exposure to the light. All barium compounds that are water or acid soluble are poisonous. Naturally occurring barium is a mixture of seven stable isotopes. Twenty two other radioactive isotopes are known to exist.

Source: CRC Handbook of Chemistry and Physics, 1913-1995. David R. Lide, Editor in Chief. Author: C.R. Hammond


Barium was first isolated by Sir Humphry Davy, an English chemist, in 1808 through the electrolysis of molten baryta (BaO). Barium is never found free in nature since it reacts with oxygen in the air, forming barium oxide (BaO), and with water, forming barium hydroxide (Ba(OH)2) and hydrogen gas (H2). Barium is most commonly found as the mineral barite (BaSO4) and witherite (BaCO3) and is primarily produced through the electrolysis of barium chloride (BaCl2).

Barium is used as a getter, a material that combines with and removes trace gases from vacuum tubes.

Barium sulfate (BaSO4), a common barium compound, is used as a filler for rubber, plastics and resins. It can be combined with zinc oxide (ZnO) to make a white pigment known as lithophone or with sodium sulfate (Na2SO4) to make another white pigment known as blanc fixe. Stones made from impure barium sulfate glow when exposed to light and will glow in the dark for up to six years if intensely heated in the presence of charcoal. These stones, known as Bologna stones, were discovered near Bologna, Italy in the early 1500s and were thought to possess magical properties by alchemists. Although all barium compounds are poisonous, barium sulfate can be safely ingested since it does not dissolve in water. It is also a good absorber of X-rays and, when swallowed, can be used to produce X-ray images of the intestinal tract.

Barium carbonate (BaCO3), another common barium compound, is used in the manufacture of ceramics and some types of glass. It is a component in clay slurries used in drilling oil wells. Barium carbonate is used to purify some chemical solutions and is the primary base material for the manufacture of other barium compounds.

Barium forms several other useful compounds. Barium nitrate (Ba(NO3)2) burns with a bright green color and is used in signal flares and fireworks. Barium chloride (BaCl) is used as a water softener. Barium oxide (BaO) easily absorbs moisture and is used as a desiccant. Barium peroxide (BaO2) forms hydrogen peroxide (H2O2) when it is mixed with water and is used as a bleaching agent that activates when wet. Barium titanate (BaTiO3) is used as a dielectric material in capacitors. Barium ferrite (BaO6Fe2O3) is used to make magnets.