Main article: Isotopes of lanthanum
iso	NA	half-life	DM	DE (MeV)	DP
¹³⁷La	syn	60,000 yrs	ε	0.600	¹³⁷Ba
¹³⁸La	0.09%	1.05×10¹¹yrs	ε	1.737	¹³⁸Ba
¹³⁸La	0.09%	1.05×10¹¹yrs	β^-	1.044	¹³⁸Ce
¹³⁹La	99.91%	La is stable with 82 neutrons

References

Lanthanum (IPA: /ˈlanθənəm/) is a chemical element in the periodic table that has the symbol La and atomic number 57.

1 Notable characteristics
2 Applications
3 History
4 Occurrence
5 Isotopes
6 References
7 External links

[edit] Notable characteristics

Image:Lanthanum.jpg

Lanthanum is a silvery white metallic element belonging to group 3 of the periodic table and often considered to be one of the lanthanides. Found in some rare-earth minerals, usually in combination with cerium and other rare earth elements. Lanthanum is malleable, ductile, and soft enough to be cut with a knife. It is one of the most reactive of the rare-earth metals. The metal reacts directly with elemental carbon, nitrogen, boron, selenium, silicon, phosphorus, sulfur, and with halogens. It oxidizes rapidly when exposed to air. Cold water attacks lanthanum slowly, while hot water attacks it much more rapidly.

[edit] Applications

Uses of lanthanum:

Carbon lighting applications, especially by the motion picture industry for studio lighting and projection.
La₂O₃ improves the alkali resistance of glass, and is used in making special optical glasses, such as:
- Infrared absorbing glass.
- Camera and telescope lenses, because of the high refractive index and low dispersion of rare-earth glasses.
Small amounts of lanthanum added to steel improves its malleability, resistance to impact and ductility.
Small amounts of lanthanum added to iron helps to produce nodular cast iron.
Small amounts of lanthanum added to molybdenum decreases the hardness of this metal and its sensitivity to temperature variations.
Mischmetal, a pyrophoric alloy used e.g. in lighter flints, contains 25% to 45% lanthanum.
Lanthanum oxide and the boride are used in electronic vacuum tubes as hot cathode materials with strong emissivity of electrons. Crystals of LaB₆ are used in high brightness, extended life, thermionic electron emission sources for scanning electron microscopes.
in Gas tungsten arc welding electrodes, as a substitute for radioactive thorium.
Hydrogen sponge alloys can contain lanthanum. These alloys are capable of storing up to 400 times their own volume of hydrogen gas in a reversible adsorption process.
Petroleum cracking catalysts.
Gas lantern mantles.
Glass and lapidary polishing compound.
La-Ba age dating of rocks and ores.
Lanthanum carbonate is used medically as a phosphate binder for the treatment of hyperphosphatemia. See details below under Biological Role.
Lanthanum nitrate is mainly applied in specialty glass, water treatment and catalyst.
Cerium activated Lanthanum bromide is the recent inorganic scintillator which has a combination of high light yield and the best energy resolution.

[edit] History

Lanthanum was discovered in 1839 by Swedish chemist Carl Gustav Mosander, when he partially decomposed a sample of cerium nitrate by heating and treating the resulting salt with dilute nitric acid. From the resulting solution, he isolated a new rare earth he called lantana. Lanthanum was isolated in relatively pure form in 1923.

The word lanthanum comes from the Greek λανθανω [lanthanō] = to lie hidden.

[edit] Occurrence

Although lanthanum belongs to chemical elements group called rare earth metals, it is not rare at all. Lanthanum is available in relatively large quantities (32 ppm in Earth’s crust).

Monazite (Ce, La, Th, Nd, Y)PO₄, and bastnasite (Ce, La, Y)CO₃F, are principal ores in which lanthanum occurs in percentages up to 25 to 38 percent.

See also category:Lanthanide minerals

[edit] Isotopes

Naturally occurring lanthanum is composed of one stable (¹³⁹La) and one radioactive (¹³⁸La) isotope, with the stable isotope, ¹³⁹La, being the most abundant (99.91% natural abundance). 38 radioisotopes have been characterized with the most stable being ¹³⁸La with a half-life of 1.05×10¹¹ years, and ¹³⁷La with a half-life of 60,000 years. All of the remaining radioactive isotopes have half-lives that are less than 24 hours and the majority of these have half lives that are less than 1 minute. This element also has 3 meta states.