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About Barium

Barium Bohr

Similarly to the adjacent element cesium within its family of the alkali metals, barium is the heaviest and most reactive of the stable elements in its family, the alkaline earths. The element first gained attention in the early 17th century in Bologna, Italy, when rocks composed of barium sulfate drew alchemists due to their unique ability to emit a phosphorescent red glow for years after being burnt and exposed to sunlight. Barium’s name is derived from the alchemical term for barium sulfate "baryta," which in turn is based on the Greek term barys meaning "heavy" or "dense" Sir Humphrey Davey bestowed the name upon his discovery of the element in 1808 via the electrolysis of molten barium salts, the same technique he used to isolate the alkali metals. Barium does not occur free in nature due to its high reactivity; it is mostly present as barium sulfate in the mineral berite (also known as barytes or heavy spar), its main commercial source; the element is also found in witherite (barium carbonate) to a lesser extent and in the fluorescent blue gemstone benitoite (barium titanium silicate), the official state gemstone of California. Natural barium is a mix of 7 different isotopes and can be produced by either electrolysis of barium chloride or the reduction of barium oxide with elemental aluminum.

Chemically similar to calcium, barium is a shiny silver metal that turns gray as its surface oxidizes in contact with air. The element is extremely electropositive and highly reactive; contact with water and alcohols causes an explosive exothermic reaction, and reactions with nonmetals such as carbon and nitrogen cause similarly exothermic reactions when heated. Because of its flammability, barium is packaged under mineral oil as a safety precaution. Additionally, soluble barium compounds are all considered extremely poisonous due to the toxicity of the Ba2+ ion and must be handled with care.

Barium has many different forms with commercially useful properties. As a metal or alloyed with aluminum, it serves as a “flashed getter” in vacuum tubes to combine with and remove residual oxygen or moisture; it can also increase the creep resistance of lead-tin alloys and enhance the structure of aluminum-silicon alloys. Barium can alloy with other metals such as zinc, lead, nickel, and tin to form intermetallic phases and alloys used as bearing alloys, deoxidizers, and (in the form of barium-nickel alloys) the basis for spark plug wires. Barium compounds such as carbonates, chlorides, oxides, hydroxides, and peroxides are used as bleaching agents, desiccants, water softeners, components of glass and ceramics, additives to oil drilling fluids, green colorings for fireworks, and rat poisons; some other applications include purification of solutions and calibration of pH equipment. Barium sulfate is uniquely insoluble in water and thus nontoxic, allowing it to be used as a radiopaque contrast media for X-ray and CAT scan imaging of the gastrointestinal tract in high purity form. The compound either by itself or in combination with zinc sulfide (a material known as lithopone) is also used as a white pigment in paints, ink, and coatings in addition to a filler for rubbers and plastics.

Some crystalline ceramic forms of barium possess unusual properties that give them specialized high technology applications. Yttrium barium copper oxide (YBCO) is a well-known high-temperature superconductor, the first material ever to be discovered that exhibits superconductivity above the temperature of liquid nitrogen (77 K). Magnetic strips of credit card and data storage devices utilize barium ferrite, a magnetic material that can take on a complex ferromagnetic fluid phase at room temperature. Barium titanate and barium zirconate (when combined, known as barium zirconate titanate or BZT) are piezoelectric, ferroelectric perovskite crystals that can function as dialectric materials in capacitors, electrolytes in solid oxide fuel cells, and nonlinear optical crystals; barium fluoride is another common optical material used in lenses, windows, and scintillators due to its wide transparency in the ultraviolet and infrared spectra.

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Barium has applications in glass, electronics, medicine, paints and colorants. Barium sulfate is opaque to x-rays and can be safely swallowed as a suspension, and thus High Purity (99.999%) Barium (Ba) Sputtering Targetit is frequently used as a contrast medium for imaging the gastrointestinal tract. Electronic coatings based on barium titanate are essential to cell phones and other microelectronics. Barium is available in both metallic and compound forms with purities from 99% to 99.999% (ACS grade to ultra-high purity). High Purity (99.9999%) Barium Oxide (BaO) Powder Elemental or metallic forms include pellets, rod, wire and granules for evaporation source material purposes. Barium oxide is an insoluble barium source available in powder and dense pellet form for such uses as optical coating and thin film applications. Barium fluoride is another insoluble form for uses in which oxygen is undesirable such as metallurgy, chemical and physical vapor deposition and in some optical coatings. Barium is also available in soluble forms including chlorides, nitrates and acetates. These compounds can be manufactured as solutions at specified stoichiometries.

Barium Properties

Barium (Ba) and molecular weight, atomic number and elemental symbolBarium is a Block S, Group 2, Period 6 element.Barium Bohr Model The number of electrons in each of Barium's shells is 2, 8, 18, 18, 8, 2 and its electron configuration is [Xe] 6s2. Elemental BariumBarium is a member of the alkaline-earth metals. The barium atom has a radius of and its Van der Waals radius is In its elemental form, CAS 7440-39-3, barium has a silvery-gray appearance. The main commercial source of barium is barite, BaSO4. Barium was discovered by Carl Wilhelm Scheele in 1772 and first isolated by Humphry Davy in 1808.

Symbol: Ba
Atomic Number: 56
Atomic Weight: 137.3
Element Category: alkaline earth metals
Group, Period, Block: 2, 6, s
Color: silvery white
Other Names: Bario
Melting Point: 727 °C, 1340.6 °F, 1000.15 K
Boiling Point: 1845 °C, 3353 °F, 2118.15 K
Density: 3.5 g/cm3
Liquid Density @ Melting Point: 3.338 g/cm3
Density @ 20°C: 3.59 g/cm3
Density of Solid: 3510 kg·m3
Specific Heat: 0.046 Cal/g/K @ 25 °C
Superconductivity Temperature: N/A
Triple Point: N/A
Critical Point: N/A
Heat of Fusion (kJ·mol-1): 7.66
Heat of Vaporization (kJ·mol-1): 150.9
Heat of Atomization (kJ·mol-1): 180.7
Thermal Conductivity: 20.184 W/cm/K @ 298.2 K
Thermal Expansion: (25 °C) 20.6 µm·m-1·K-1
Electrical Resistivity: (20 °C) 332 nΩ·m
Tensile Strength: N/A
Molar Heat Capacity: 28.07 J·mol-1·K-1
Young's Modulus: 13 GPa
Shear Modulus: 4.9 GPa
Bulk Modulus: 9.6 GPa
Poisson Ratio: N/A
Mohs Hardness: 1.25
Vickers Hardness: N/A
Brinell Hardness: N/A
Speed of Sound: (20 °C) 1620 m·s-1
Pauling Electronegativity: 0.89
Sanderson Electronegativity: 0.68
Allred Rochow Electronegativity: 0.97
Mulliken-Jaffe Electronegativity: 0.88 (sp orbital)
Allen Electronegativity: N/A
Pauling Electropositivity: 3.11
Reflectivity (%): N/A
Refractive Index: N/A
Electrons: 56
Protons: 56
Neutrons: 81
Electron Configuration: [Xe] 6s2
Atomic Radius: 222 pm
Atomic Radius,
non-bonded (Å):
Covalent Radius: 215±11 pm
Covalent Radius (Å): 2.06
Van der Waals Radius: 268 pm
Oxidation States: 2
Phase: Solid
Crystal Structure: body-centered cubic
Magnetic Ordering: paramagnetic
Electron Affinity (kJ·mol-1) 13.949
1st Ionization Energy: 502.86 kJ·mol-1
2nd Ionization Energy: 965.24 kJ·mol-1
3rd Ionization Energy: N/A
CAS Number: 7440-39-3
EC Number: 231-149-1
MDL Number: MFCD00134031
Beilstein Number: N/A
SMILES Identifier: [Ba]
InChI Identifier: InChI=1S/Ba
PubChem CID: 5355457
ChemSpider ID: 4511436
Earth - Total: 4.0 ppm
Mercury - Total: 3.1 ppb
Venus - Total: 4.2 ppb
Earth - Seawater (Oceans), ppb by weight: 30
Earth - Seawater (Oceans), ppb by atoms: 1.4
Earth -  Crust (Crustal Rocks), ppb by weight: 340000
Earth -  Crust (Crustal Rocks), ppb by atoms: 51000
Sun - Total, ppb by weight: 10
Sun - Total, ppb by atoms: 0.1
Stream, ppb by weight: 25
Stream, ppb by atoms: 0.2
Meterorite (Carbonaceous), ppb by weight: 2800
Meterorite (Carbonaceous), ppb by atoms: 410
Typical Human Body, ppb by weight: 300
Typical Human Body, ppb by atom: 14
Universe, ppb by weight: 10
Universe, ppb by atom: 0.09
Discovered By: Carl Wilhelm Scheele
Discovery Date: 1772
First Isolation: Humphry Davy (1808)

Health, Safety & Transportation Information for Barium

Barium powder can ignite spontaneously in air, and when Barium compounds are water or acid soluble, they are very poisonous. Safety data for Barium and its compounds can vary widely depending on the form. For potential hazard information, toxicity, and road, sea and air transportation limitations, such as DOT Hazard Class, DOT Number, EU Number, NFPA Health rating and RTECS Class, please see the specific material or compound referenced in the Products tab. The below information applies to elemental (metallic) Barium.

Safety Data
Material Safety Data Sheet MSDS
Signal Word Danger
Hazard Statements H261-H315-H319-H335
Hazard Codes F,Xi
Risk Codes 11-14/15-36/37/38
Safety Precautions 16-26-36/37-43
RTECS Number CQ8370000
Transport Information UN 1400 4.3/PG 2
WGK Germany 3
Globally Harmonized System of
Classification and Labelling (GHS)
Exclamation Mark-Acute Toxicity Flame-Flammables

Barium Isotopes

Barium has six stable isotopes: 132Ba, 134Ba, 135Ba, 136Ba, 137Ba, and 138Ba.

Nuclide Isotopic Mass Half-Life Mode of Decay Nuclear Spin Magnetic Moment Binding Energy (MeV) Natural Abundance
(% by atom)
114Ba 113.95068(15) 530(230) ms [0.43(+30-15) s] β+ + p to 114Xe; β+ to 114Cs; β+ + α to 110I 0+ N/A 904.72 -
115Ba 114.94737(64)# 0.45(5) s β+ to 115Cs; β+ + p to 114Xe (5/2+)# N/A 922.11 -
116Ba 115.94138(43)# 1.3(2) s β+ to 116Cs; β+ + p to 115Xe 0+ N/A 930.19 -
117Ba 116.93850(32)# 1.75(7) s β+ to 117Cs; β+ + α to 113I; β+ + p to 116Xe (3/2)(+#) N/A 947.59 -
118Ba 117.93304(21)# 5.2(2) s β+ to 118Cs; β+ + p to 117Xe 0+ N/A 955.67 -
119Ba 118.93066(21) 5.4(3) s β+ to 119Cs; β+ + p to 118Xe (5/2+) N/A 963.74 -
120Ba 119.92604(32) 24(2) s β+ to 120Cs 0+ N/A 981.14 -
121Ba 120.92405(15) 29.7(15) s β+ to 121Cs; β+ + p to 120Xe 5/2(+) N/A 989.22 -
122Ba 121.91990(3) 1.95(15) min β+ to 122Cs 0+ N/A 1006.61 -
123Ba 122.918781(13) 2.7(4) min β+ to 123Cs 5/2(+) N/A 1014.69 -
124Ba 123.915094(13) 11.0(5) min β+ to 124Cs 0+ N/A 1022.77 -
125Ba 124.914473(12) 3.5(4) min β+ to 125Cs 1/2(+#) N/A 1030.85 -
126Ba 125.911250(13) 100(2) min β+ to 126Cs 0+ N/A 1038.93 -
127Ba 126.911094(12) 12.7(4) min β+ to 127Cs 1/2+ N/A 1047.01 -
128Ba 127.908318(11) 2.43(5) d EC to 128Cs 0+ N/A 1064.4 -
129Ba 128.908679(12) 2.23(11) h EC to 129Cs 1/2+ -0.4 1072.48 -
130Ba 129.9063208(30) 1.6 x 1021 y 2EC to 130Xe 0+ N/A 1080.56 0.106
131Ba 130.906941(3) 11.50(6) d EC to 131Cs 1/2+ 0.7081 1088.64 -
132Ba 131.9050613(11) Observationally Stable - 0+ N/A 1096.72 0.101
133Ba 132.9060075(11) 10.51(5) y EC to 133Cs 1/2+ 0.7717 1104.8 -
134Ba 133.9045084(4) STABLE - 0+ N/A 1112.87 2.417
135Ba 134.9056886(4) STABLE - 3/2+ 0.837943 1120.95 6.592
136Ba 135.9045759(4) STABLE - 0+ N/A 1129.03 7.854
137Ba 136.9058274(5) STABLE - 3/2+ 0.937365 1137.11 11.232
138Ba 137.9052472(5) STABLE - 0+ N/A 1145.19 71.698
139Ba 138.9088413(5) 83.06(28) min β- to 139La 7/2- -0.97 1153.27 -
140Ba 139.910605(9) 12.752(3) d β- to 140La 0+ N/A 1152.03 -
141Ba 140.914411(9) 18.27(7) min β- to 141La 3/2- N/A 1160.11 -
142Ba 141.916453(7) 10.6(2) min β- to 142La 0+ N/A 1168.19 -
143Ba 142.920627(14) 14.5(3) s β- to 143La 5/2- N/A 1166.95 -
144Ba 143.922953(14) 11.5(2) s β- to 144La 0+ N/A 1175.03 -
145Ba 144.92763(8) 4.31(16) s β- to 145La 5/2- N/A 1183.11 -
146Ba 145.93022(8) 2.22(7) s β- to 146La; β- + n to 145La 0+ N/A 1181.87 -
147Ba 146.93495(22)# 0.893(1) s β- to 147La; β- + n to 146La (3/2+) N/A 1189.95 -
148Ba 147.93772(9) 0.612(17) s β- to 148La; β- + n to 147La 0+ N/A 1198.03 -
149Ba 148.94258(21)# 344(7) ms β- to 149La; β- + n to 148La 3/2-# N/A 1196.79 -
150Ba 149.94568(43)# 300 ms β- to 150La 0+ N/A 1204.87 -
151Ba 150.95081(43)# 200# ms [>300 ns] β- to 151La 3/2-# N/A 1203.63 -
152Ba 151.95427(54)# 100# ms β- to 152La 0+ N/A 1211.71 -
153Ba 152.95961(86)# 80# ms β- to 153La 5/2-# N/A 1219.79 -