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|Appearance||silvery gray; with a pale yellow tint|
|Standard atomic weight (Ar, standard)||137.327(7)|
|Barium in the periodic table|
|Atomic number (Z)||56|
|Group||group 2 (alkaline earth metals)|
|Element category||alkaline earth metals|
|Electron configuration||[Xe] 6s2|
Electrons per shell
|2, 8, 18, 18, 8, 2|
|Phase at STP||Ba: Solid|
|Melting point||1000 K (727 °C, 1341 °F)|
|Boiling point||2118 K (1845 °C, 3353 °F)|
|Density (near r.t.)||3.51 g/cm3|
|when liquid (at m.p.)||3.338 g/cm3|
|Heat of fusion||7.12 kJ/mol|
|Heat of vaporization||142 kJ/mol|
|Molar heat capacity||28.07 J/(mol·K)|
|Oxidation states||+1, +2 (a strongly basic oxide)|
|Electronegativity||Pauling scale: 0.89|
|Atomic radius||empirical: 222 pm|
|Covalent radius||215±11 pm|
|Van der Waals radius||268 pm|
|Spectral lines of barium|
|Natural occurrence||Ba: Primordial|
|Crystal structure||body-centered cubic (bcc)|
|Speed of sound thin rod||1620 m/s (at 20 °C)|
|Thermal expansion||20.6 µm/(m·K) (at 25 °C)|
|Thermal conductivity||18.4 W/(m·K)|
|Electrical resistivity||332 nΩ·m (at 20 °C)|
|Magnetic susceptibility||+20.6·10−6 cm3/mol|
|Young's modulus||13 GPa|
|Shear modulus||4.9 GPa|
|Bulk modulus||9.6 GPa|
|Discovery||Carl Wilhelm Scheele (1772)|
|First isolation||Humphry Davy (1808)|
|Main isotopes of barium|
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.
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.
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.
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.
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.
As a metal
As chemical compounds
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.
Barium is a very toxic element, though, 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.
- Meija, J.; Coplen, T. B.; Berglund, M.; Brand, W.A.; De Bièvre, P.; Gröning, M.; Holden, N.E.; Irrgeher, J. et al. (2016). "Atomic weights of the elements 2013 (IUPAC Technical Report)". Pure and Applied Chemistry 88 (3): 265-91. . https://www.degruyter.com/downloadpdf/j/pac.2016.88.issue-3/pac-2015-0305/pac-2015-0305.xml.
- Lide, D. R., ed. (2005). "Magnetic susceptibility of the elements and inorganic compounds". CRC Handbook of Chemistry and Physics (86th ed.). Boca Raton (FL): CRC Press. . https://web.archive.org/web/20110303222309/http://www-d0.fnal.gov/hardware/cal/lvps_info/engineering/elementmagn.pdf.
- Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E110. .