Barium: the essentials
Barium is a metallic element, soft, and when pure is silvery white like lead. The metal oxidises very easily and it reacts with water or alcohol. Barium is one of the alkaline-earth metals. Small amounts of barium compounds are used in paints and glasses.
Barium salts impart green colours to flames. The picture above shows the colour arising from adding barium chlorate (BaClO3) to a burning mixture (only to be carried out by a professionally qualified chemist).
Image adapted with permission from Prof James Marshall's (U. North Texas, USA) Walking Tour of the elements CD.
Barium: historical information
Baryta (barium oxide, BaO) was distinguished from lime (calcium oxide, CaO) by Scheele in 1774. Elemental barium was isolated by Sir Humphrey Davy in 1808 who electrolysed molten baryta.
Sometime prior to the autumn of 1803, the Englishman John Dalton was able to explain the results of some of his studies by assuming that matter is composed of atoms and that all samples of any given compound consist of the same combination of these atoms. Dalton also noted that in series of compounds, the ratios of the masses of the second element that combine with a given weight of the first element can be reduced to small whole numbers (the law of multiple proportions). This was further evidence for atoms. Dalton's theory of atoms was published by Thomas Thomson in the 3rd edition of his System of Chemistry in 1807 and in a paper about strontium oxalates published in the Philosophical Transactions. Dalton published these ideas himself in the following year in the New System of Chemical Philosophy. The symbol used by Dalton for barium is shown below. [See History of Chemistry, Sir Edward Thorpe, volume 1, Watts & Co, London, 1914.]
Barium around us Read more »
Barium has no biological role. The British Pharmaceutical Codex from 1907 indicates that barium chloride ["barii chloridum", BaCl2.2H2O] has a stimulant action on the heart and other muscles. It was said that it "raises blood pressure by constricting the vessels and tends to empty the intestines, bladder, and gall bladder". Its poisonous nature was also pointed out. Barium sulphide (BaS) was used as a depilatory agent (removes hair). Barium sulphate (BaSO4) is insoluble and used for body imaging (barium meal).
Elemental barium is never found in nature. Barium mainly is found in the ores barite and to a lesser extent in witherite.
|Location||ppb by weight||ppb by atoms||Links|
|Human||300 ppb by weight||14 atoms relative to C = 1000000|
Physical properties Read more »
Heat properties Read more »
- Melting point: 1000 [727 °C (1341 °F)] K
- Boiling point: 2143 [1870 °C (3398 °F)] K
- Enthalpy of fusion: |203| kJ mol-1
Crystal structure Read more »
The solid state structure of barium is: bcc (body-centred cubic).
Barium: orbital properties Read more »
Barium atoms have 56 electrons and the shell structure is 22.214.171.124.8.2. The ground state electronic configuration of neutral Barium is [Xe].6s2 and the term symbol of Barium is 1S0.
- Pauling electronegativity: 0.89 (Pauling units)
- First ionisation energy: 502.9 kJ mol‑1
- Second ionisation energy: 965.2 kJ mol‑1
Isolation: barium metal is available commercially and there is normally no need to make it in the laboratory. Commercially, it is made on small scale by the electrolysis of molten barium chloride, BaCl2.
cathode: Ba2+(l) + 2e- → Ba
anode: Cl-(l) → 1/2Cl2 (g) + e-
Barium metal can also be islated from the reduction of barium oxide, BaO, with aluminium.
6BaO + 2Al→ 3Ba + Ba3Al2O6
Barium isotopes Read more »
Barium isotopes are used in a wide variety of fields and applications. Ba-130 is used in the production of Ba-131/Cs-131 which is used in brachytherapy (seeds). Ba-132 can be used for the production of Ba-133 which is used as a gamma reference source. Ba-134 has been used to perform experiments in the field of nuclear physics. Ba-136 has been used to study photon scattering phenomena. Both Ba-136 and Ba-138 have been used in activation cross section experiments. Ba-135 has been used to validate the use of spinor symmetry while Ba-137 has been used in experiments regarding the theory of relativistic coupled clusters. Finally, Ba-138 has been used in studying so-called r- and s-processes in stars.
|130Ba||129.906282 (8)||0.106 (1)||0|
|132Ba||131.905042 (9)||0.101 (1)||0|
|134Ba||133.904486 (7)||2.417 (18)||0|
|135Ba||134.905665 (7)||6.592 (12)||3/2||0.837943|
|136Ba||135.904553 (7)||7.854 (24)||0|
|137Ba||136.905812 (6)||11.232 (24)||3/2||0.937365|
|138Ba||137.905232 (6)||71.698 (42)||0|