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56Ba137.33

Element 56, an alkaline earth metal

Barium

Heavy by name and poisonous as a soluble salt, yet swallowed safely as a white paste so doctors can X-ray the gut.

At a glance

Symbol
Ba
Atomic number
56
Average atomic mass
137.33
Group
2
Period
6
Family
alkaline earth metal
Electron configuration
[Xe] 6s²
Valence electrons
2
Electronegativity
0.89
Common ions
Ba²⁺

On the table

Periodic table with Barium highlighted123456789101112131415161718123456757-7189-103HHeLiBeBCNOFNeNaMgAlSiPSClArKCaScTiVCrMnFeCoNiCuZnGaGeAsSeBrKrRbSrYZrNbMoTcRuRhPdAgCdInSnSbTeIXeCsBaLaCePrNdPmSmEuGdTbDyHoErTmYbLuHfTaWReOsIrPtAuHgTlPbBiPoAtRnFrRaAcThPaUNpPuAmCmBkCfEsFmMdNoLrRfDbSgBhHsMtDsRgCnNhFlMcLvTsOg

Period 6, group 2. The other alkaline earth metals are tinted, and every cell opens its own article.

Electrons and bonding

Ba

Two valence electrons, which barium gives up to form the Ba²⁺ ion in its compounds.

Properties

State at 25 °C
solid
What it looks like
soft, silvery-white metal that tarnishes quickly
Melting point
727 °C
Boiling point
1897 °C
Density
3.62 g/cm³
Flame test
apple green

Where it is found

Mined mostly as barite (BaSO₄), in China, India and Morocco, and as witherite (BaCO₃).

Discovery and name

Carl Wilhelm Scheele identified baryta, barium oxide, as a new earth in 1774, and Humphry Davy isolated the metal in 1808 by electrolysis. The name comes from the Greek barys, heavy, after the dense mineral barite.

What it is used for

Most barite is ground up for drilling mud, where its weight keeps oil and gas wells under control. Barium sulfate, which does not dissolve, is swallowed or given as an enema so the digestive tract shows up on X-rays. Barium compounds also make green fireworks, and barium goes into glass, ceramics and spark plugs.

In compounds

BaSO₄barium sulfate, barite and X-ray contrastBaCO₃barium carbonate, witheriteBa(NO₃)₂barium nitrate, green fireworksBaTiO₃barium titanate, in capacitorsBaCl₂barium chloride

Handle with care

Barium compounds that dissolve in water, such as barium chloride and barium carbonate, are poisonous. Barium sulfate is safe for X-rays only because it does not dissolve.