Stable isotopes of barium available from ISOFLEX
|Isotope||Z(p)||N(n)||Atomic Mass||Natural Abundance||Enrichment Level||Chemical Form|
Barium was discovered in 1808 by Sir Humphry Davy. Its name derives from the Greek word barys, meaning “heavy.”
A silvery-white, soft, ductile and somewhat malleable metal, barium gives off a green color in flame. It is extremely reactive and readily reacts with water, ammonia, halogens, oxygen and most acids. Barium metal reacts exothermically with oxygen at ambient temperatures, forming barium oxide; the reaction is especially violent when the metal is present in powder form. Barium also reacts violently with water, forming barium hydroxide and liberating hydrogen. It reacts violently with dilute acids, evolving hydrogen.
Barium is a strong reducing agent. It reduces oxidizing agents, reacting violently. It also combines with several metals — including aluminum, zinc, lead and tin — forming a wide range of intermetallic compounds and alloys.
The most important use of barium is as a scavenger in electronic tubes. The metal, often in powder form or as an alloy with aluminum, is employed to remove the last traces of gases from vacuum and television picture tubes. Alloys of barium have numerous applications, including battery performance and deoxidizing alloys to lower the oxygen content. Thin films of barium are used as lubricants on the rotors of anodes in vacuum x-ray tubes, as well as on alloys used for spark plugs. A few radioactive isotopes of barium find applications in nuclear reactions and spectrometry.
Finely divided barium powder is pyrophoric. It can explode in contact with air or oxidizing gases. It is likely to explode when mixed and stirred with halogenated hydrocarbon solvents. All barium salts, especially the water- and acid-soluble compounds, are highly toxic. Barium ion is a stimulant to the heart muscle and can cause death through ventricular fibrillation of the heart. Intake of a few grams of barium salt can be lethal to humans. The insoluble salts such as barium sulfate, however, have little toxic action.
Properties of Barium
|Standard state||Solid at 298 ºK|
|CAS Registry ID||7440-39-3|
|Group in periodic table||2|
|Group name||Alkaline earth metals|
|Period in periodic table||6|
|Block in periodic table||s-block|
|Melting point||727 °C|
|Boiling point||1845 °C|
|Vaporization point||1897 ºC|
|Thermal conductivity||18.4 W/(m·K)|
|Electrical resistivity||332 µΩ·cm at 20°C|
|Heat of vaporization||140.3 kJ·mol-1|
|Heat of fusion||8 kJ·mol-1|
|Density of liquid||3.338 g/cm3|
|Density of solid||3.51 g/cm3|
|Atomic radius||222 pm|
|Ionic radius||Ba2+ in crystal: 1.42 Å (coordination number 8)|
|First ionization potential||10.00 eV|