PTL:Barium
From ChemEd Collaborative
Barium is a metal in Group IIA - the alkaline earth metals - in the 6th period. Other elements in this group are beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), and radium (Ra).
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Discovered
The element was discovered in 1808 by Davy, who electrolyzed molten barium salts.
Name
The name is derived from the Greek word barys, which means heavy, and the symbol Ba is derived from the name.
Characteristics
Barium is the metal in barite (heavy spar, BaSO4), a very dense mineral (4.5 g/cm3).
Barium is a metallic element, soft, and when pure is silvery-white like lead. It belongs to the alkaline earth group, resembling calcium chemically.
Found
It is found only in combination with other elements, chiefly in barite (BaSO4) and witherite (BaCO3).
Prepared
and is prepared by electrolysis of the chloride or (industrially) by reduction of BaO by aluminum.
Reactions
Like the other alkaline earth metals, it reacts readily with air to give barium peroxide,
Ba(s) + O2(g) 
BaO2(s)
water to give barium hydroxide,
Ba(s) + 2 H2O Ba(OH)2 + H2(g)
and acids to give Ba2+ salts. For example,
Ba(s) + 2 HCl(aq) BaCl2(aq) + H2(g)
Notice that Ba(NO3)2 is not very soluble.
Uses
The metal is used in a variety of alloys. 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. For this reason the metal is used as a "[getter]" to remove water and oxygen from vacuum tubes.
The most important compounds are the peroxide (BaO2), which is produced when the metal burns in air, the chloride, the sulfate, the carbonate, the nitrate, and the chlorate.
Lithopone, a paint pigment containing barium sulfate and zinc sulfide, has good covering power, and does not darken in the presence of sulfides. The pure sulfate is also used in paint because BaSO4 is sufficiently insoluble to be nonpoisonous. It is used in [x-ray diagnostic work], where it coats the intestinal tract and intensify the image. The carbonate is used as a rat poison and in glass, while the [nitrate and chlorate give green colors in fireworks]. The impure sulfide phosphoresces after exposure to the light. The compounds and the metal are not expensive.
All barium compounds that are water or acid soluble are poisonous because the Ba2+ ion is a muscle stimulant.
Emission Spectra
This is the emission spectra for Barium.
