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Barium, 56Ba
Barium unter Argon Schutzgas Atmosphäre.jpg
Pronunciation/ˈbɛəriəm/ (BAIR-ee-əm)
Appearancesilvery gray; with a pale yellow tint[1]
Standard atomic weight Ar, std(Ba)137.327(7)[2]
Barium in the periodic table
Hydrogen Helium
Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon
Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon
Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon
Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon
Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson


Atomic number (Z)56
Groupgroup 2 (alkaline earth metals)
Periodperiod 6
Block  s-block
Electron configuration[Xe] 6s2
Electrons per shell2, 8, 18, 18, 8, 2
Physical properties
Phase at STPsolid
Melting point1000 K ​(727 °C, ​1341 °F)
Boiling point2118 K ​(1845 °C, ​3353 °F)
Density (near r.t.)3.51 g/cm3
when liquid (at m.p.)3.338 g/cm3
Heat of fusion7.12 kJ/mol
Heat of vaporization142 kJ/mol
Molar heat capacity28.07 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
Oxidation states+1, +2 (a strongly basic oxide)
ElectronegativityPauling scale: 0.89
Ionization energies
  • 1st: 502.9 kJ/mol
  • 2nd: 965.2 kJ/mol
  • 3rd: 3600 kJ/mol
Atomic radiusempirical: 222 pm
Covalent radius215±11 pm
Van der Waals radius268 pm
Color lines in a spectral range
Spectral lines of barium
Other properties
Natural occurrenceprimordial
Crystal structurebody-centered cubic (bcc)
Body-centered cubic crystal structure for barium
Speed of sound thin rod1620 m/s (at 20 °C)
Thermal expansion20.6 µm/(m⋅K) (at 25 °C)
Thermal conductivity18.4 W/(m⋅K)
Electrical resistivity332 nΩ⋅m (at 20 °C)
Magnetic orderingparamagnetic[3]
Molar magnetic susceptibility+20.6·10−6 cm3/mol[4]
Young's modulus13 GPa
Shear modulus4.9 GPa
Bulk modulus9.6 GPa
Mohs hardness1.25
CAS Number7440-39-3
DiscoveryCarl Wilhelm Scheele (1772)
First isolationHumphry Davy (1808)
Main isotopes of barium
Iso­tope Abun­dance Half-life (t1/2) Decay mode Pro­duct
130Ba 0.11% (0.5–2.7)×1021 y εε 130Xe
132Ba 0.10% stable
133Ba syn 10.51 y ε 133Cs
134Ba 2.42% stable
135Ba 6.59% stable
136Ba 7.85% stable
137Ba 11.23% stable
138Ba 71.70% stable
 Category: Barium
| references
Corroded barium metal

Barium is chemical element 56 on the periodic table. Its symbol is Ba. It contains 56 protons and 56 electrons. Its mass number is about 137.3. It is a metal.

Properties[change | change source]

Physical properties[change | change source]

Barium is part of a group of elements known as the alkaline earth metals. It is a silvery metal that easily turns black. It is soft and ductile. It can form alloys with some metals that are partially alloys and partially chemical compounds.

Chemical properties[change | change source]

Barium is reactive, and if you put pure barium metal in the air, it will react with oxygen. At first it will turn black, then white as barium oxide is formed. Barium reacts with water to make barium hydroxide and hydrogen gas. Barium also reacts very fast with acids to make a barium salt and hydrogen. Barium can form barium peroxide if it is burned in air.

Barium reacts with many other metal oxides and sulfides to make barium oxide or sulfide and the metal. It also reacts with carbon and nitrogen at a high temperature to make barium cyanide.

Chemical compounds[change | change source]

Barium is too reactive as a metal, so it is not found in the earth as a metal. It is found in chemical compounds. Barium only occurs in one oxidation state: +2. Most barium compounds are colorless. The ones that dissolve in water or stomach acid are very toxic. Barium sulfate is well known because it does not dissolve in water or acids. Barium compounds are quite heavy. Barium compounds put out a greenish flame when heated red-hot.

Occurrence[change | change source]

Barium sulfate as barite

Barium is found as barium sulfate (barite) and barium carbonate (witherite) in the ground. Both of these minerals do not dissolve in water. Barium sulfate hardly dissolves in anything. Barium is found mainly in China, Germany, India, Morocco, and the US.

Preparation[change | change source]

It is very hard to get barium from barium sulfate. So barium sulfate is reduced by carbon to make barium sulfide and carbon dioxide. The barium sulfide is dissolved in hydrochloric acid. This makes hydrogen sulfide and barium chloride. The barium chloride is melted and electrolyzed to get liquid barium metal. The barium metal is solidified and stored in oil.

Barium carbonate, the other ore of barium, is dissolved in hydrochloric acid to make barium chloride and carbon dioxide. The barium chloride is melted and electrolyzed, making barium metal.

Uses[change | change source]

As a metal[change | change source]

Barium is used to remove oxygen from cathode ray tubes and vacuum tubes. It is placed inside and reacts with all of the oxygen, using it up. Barium is also used in spark plug wire.

As chemical compounds[change | change source]

Certain compounds of barium, such as barium sulfate, are not toxic and can be put in the body. We can see where the barium travels in the body by X-rays and this can tell us whether there are problems, such as blockages. The barium sulfate builds up inside the body accumulating in organ systems. Barium sulfate absorbs the X-Rays as they pass through the body and an image is formed from the points where the rays have not passed through. It is useful because it provides a reasonably detailed image from very limited radiation exposure, compared with a CT scan for instance. Barium sulfate can be used as a pigment, too.

Other barium compounds have several other uses.

Safety[change | change source]

Barium is a very toxic element, and is dangerous. There is a really small amount of barium in our food, and this does not cause problems. If we get barium from other places, though, it can cause many problems. Even 1 gram of barium can kill you. It is dangerous because it acts like other really important elements, such as calcium and magnesium. If barium replaces these elements, it messes up the body.[needs to be explained]

References[change | change source]

  1. Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 112. ISBN 978-0-08-037941-8.
  2. "Standard Atomic Weights: Barium". CIAAW. 1985.
  3. Lide, D. R., ed. (2005). "Magnetic susceptibility of the elements and inorganic compounds". CRC Handbook of Chemistry and Physics (PDF) (86th ed.). Boca Raton (FL): CRC Press. ISBN 0-8493-0486-5.
  4. Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E110. ISBN 0-8493-0464-4.