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56 Ba 137.327(7)

Barium

Alkaline earth metal
Symbol Ba
Atomic Number 56
Atomic Weight 137.327(7)
CAS Registry ID 7440-39-3
Group Name Alkaline earth metal
Period Number 6
Block s-block
State at STP Solid

Description

Sample of Barium ⌕ Enlarge Image

Barium is an alkaline earth metal that is a silvery white solid in its natural state. It is a soft metal that is very reactive in air. Barium has an atomic weight of 137.327, a melting point of 1341 °F, and a boiling point of 3447 °F. Some common uses of barium include: as a compound for drilling mud and oil wells, as a sulfate in x-ray imaging, as an alloy with nickel in spark plug wire, as a component in glassmaking processes, as a carbonate in brick making, and in the production of rubber.

Isolation

Barium does not occur in nature in its free form, and isolation processes are used to extract barium for commercial purposes.

Barium ⌕ Enlarge Image

Barium occurs in nature in mineral form. The most common minerals which contain barium are barite, a barium sulfate, and witherite which contains barium carbonate. The extraction process of barium is complicated because barium is so reactive with air; isolated barium oxidizes quickly in the air and so its pure form is not used very often. For commercial barium uses, barium is isolated from the mineral barite. The isolation process uses electrolysis of melted barium chloride to yield pure barium. Barium chloride is formed from the barium sulfate. Molten barium chloride serves as the cathode and the chlorine serves as the anode; electrolysis of these elements causes separation. Another isolation process reduced barium oxide by reacting it with aluminum on a 6 to 2 basis. The result from this reduction process is pure barium and a barium aluminum oxide compound. Pure barium has to be stored carefully to prevent it from being oxidized by air.

General

NameBarium
SymbolBa
Number56
Chemical seriesAlkaline earth metal
Group2
Period6
Blocks
Appearancesilvery white
Standard atomic weight137.327(7) g·mol⁻¹
Electron configuration[Xe] 6s2
Electrons per shell2, 8, 18, 18, 8, 2

Atomic Properties

Crystal structurecubic body centered
Oxidation states2 (strongly basic oxide)
Electronegativity0.89 (scale Pauling)
Ionization energies1st: 502.9 kJ/mol
2nd: 965.2 kJ/mol
3rd: 3600 kJ/mol
Atomic radius215 pm
Atomic radius (calc.)253 pm
Covalent radius198 pm
Van der Waals radius

Physical Properties

Phasesolid
Density (near r.t.)3.51  g·cm−3
Liquid density at m.p.3.338  g·cm−3
Melting point1000 K (727 °C, 1341 °F)
Boiling point2170 K (1897 °C, 3447 °F)
Critical point
Heat of fusion7.12  kJ·mol−1
Heat of vaporization140.3  kJ·mol−1
Heat capacity(25 °C) 28.07  J·mol−1·K−1

Miscellaneous

Magnetic orderingparamagnetic
Electrical resistivity(20 °C) 332 n Ω·m
Thermal conductivity(300 K) 18.4  W·m−1·K−1
Thermal expansion(25 °C) 20.6  µm·m−1·K−1
Speed of sound (thin rod)(20 °C) 1620 m/s
Young's modulus13 GPa
Shear modulus4.9 GPa
Bulk modulus9.6 GPa
Poisson ratio
Mohs hardness1.25
Vickers hardness
Brinell hardness