Barium

Barium - Ba

CAS: 7440-39-3
Description: Soft, heavy, silver-colored metal
Classification: Alkaline Earth
Date of Discovery: 1808
Discoverer: Sir Humphrey Davy
Name Origin: Greek barys "heavy"

Atomic Number: 56
Number of Neutrons: 81
Atomic Mass: 137.327(7) amu
Melting Point: 727 °C
Boiling Point: 1897 °C
Density (293 K): 3.5 g/cm³
Atomic volume: 39.24 cm³/mol
Electrical resistivity: 0.030 10^-6/cm

Thermal conductivity: 0.184 W/cmK
Enthalpy of atomization: 175.7 kJ/mol
Enthalpy of vaporization: 142.0 kJ/mol
Enthalpy of fusion: 7.750 kJ/mol
Specific heat capacity: 0.204 J/gK

Energy levels: 2-8-18-18-8-2
Electron configuration: [Xe]6s²
Crystal Structure: Cubic body centered
Atomic radius: 2.78 Å
Covalent radius: 1.98 Å
Oxidation States: +2
Electronegativity, Pauling: 0.89
Electron affinity: 0.15 eV
First ionization energy: 5.212 eV
2nd ionization energy: 10.004 eV
3rd ionization energy:
Polarizability: 39.7 10^-24cm³

Isotope	Natural Abundance	Atomic Mass	Half-life	Decay Mode	Spin
¹¹⁷Ba	116.9377	1.8 s	⁺, EC	(3/2-)
¹¹⁹Ba	118.931	5.4 s	⁺, EC
¹²⁰Ba	119.9260	24 s	⁺, EC	0+
¹²¹Ba	120.9245	30 s	⁺, EC	5/2
¹²²Ba	121.9203	2.0 m	⁺, EC	0+
¹²³Ba	122.9189	2.7 m	⁺, EC
¹²⁴Ba	123.91509	12 m	⁺, EC
^125mBa	8 m	⁺, EC
¹²⁵Ba	124.9146	3.5 m	⁺, EC	1/2+
¹²⁶Ba	125.91124	1.65 h	⁺; EC	0+
¹²⁷Ba	126.9111	12.9 m	⁺; EC	1/2+
¹²⁸Ba	127.90831	2.43 d	EC	0+
^129mBa	2.17 h	EC; ⁺	7/2+
¹²⁹Ba	128.90868	2.2 h	⁺; EC	1/2+
¹³⁰Ba	0.106(2)	129.90631	Stable	0+
^131mBa	14.6 m	IT	9/2-
¹³¹Ba	130.90693	11.7 d	EC	1/2+
¹³²Ba	0.101(3)	131.905056	Stable	0+
^133mBa	1.621 d	IT	11/2-
¹³³Ba	132.906003	10.53 y	EC	1/2+
¹³⁴Ba	2.417(27)	133.904504	Stable	0+
^135mBa	1.2 d	IT	11/2-
¹³⁵Ba	6.592(18)	134.905684	Stable	3/2+
^136mBa	0.308 s	IT	7-
¹³⁶Ba	7.854(36)	135.904571	Stable	0+
^137mBa	2.552 m	IT	11/2-
¹³⁷Ba	11.23(4)	136.905822	Stable	3/2+
¹³⁸Ba	71.70(7)	137.905242	Stable	0+
¹³⁹Ba	138.908836	1.396 h	^-	7/2-
¹⁴⁰Ba	139.91060	12.75 d	^-	0+
¹⁴¹Ba	140.91441	18.3 m	^-	3/2-
¹⁴²Ba	141.91645	10.7 m	^-	0+
¹⁴³Ba	142.92061	14.3 s	^-	5/2+
¹⁴⁴Ba	143.92294	11.4 s	^-	0+
¹⁴⁵Ba	144.9269	4.0 s	^-	(5/2-)
¹⁴⁶Ba	145.9302	2.20 s	^-	0+
¹⁴⁷Ba	146.9340	0.892 s	^-
¹⁴⁸Ba	147.9377	0.64 s	^-, n
¹⁴⁹Ba	148.9421	0.36 s	^-, (n)
Baryta was distinguished from lime by Scheele in 1774; the element was discovered by Sir Humphrey Davy in 1808. It is found only in combination with other elements, chiefly in barite or heavy spar (BaSO₄) and witherite (BaCO₃) and is prepared by electrolysis of the chloride. Barium is a metallic element, soft, and when pure is silvery white like lead; it belongs to the alkaline earth group, resembling calcium chemically. 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. The metal is used as a "getter" in vacuum tubes. The most important compounds are the peroxide (BaO₂), chloride, sulfate, carbonate, nitrate, and chlorate. Lithopone, a pigment containing barium sulfate and zinc sulfide, has good covering power, and does not darken in the presence of sulfides. The sulfate, as permanent white or blanc fixe, is also used in paint, in X-ray diagnostic work, and in glassmaking. Barite is extensively used as a weighting agent in oilwell drilling fluids, and also in making rubber. The carbonate has been used as a rat poison, while the nitrate and chlorate give colors in pyrotechny. 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. Naturally occurring barium is a mixture of seven stable isotopes. Thirty-nine other radioactive isotopes and isomers are known to exist. LINKS: Barium Enema Barium GI Formation of Giant Barium and Tc-poor S stars Return Sources for the information on this website include: Lide, David R., ed. CRC Handbook of Chemistry and Physics, 78th Ed., 1997-1998.

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