Atomic number: 57
Year discovered: 1839
Discovered by: Carl Gustaf Mosander (1797-1858), a Swedish chemist.
- Carl Mosander recognized the element lanthanum in impure cerium nitrate in 1839.
- While studying a compound of cerium, he found a new element which he named lanthanum from a Greek word meaning “hidden”, because it had been hidden so effectively in those minerals.
- His extraction resulted in oxide lanthana.
- A number of other lanthanides (rare-earths) were later discovered by the identification of the impurities in yttrium and cerium compounds.
- Lanthanum is silvery white, malleable, ductile, and soft enough to be cut with a knife.
- It is one of the most reactive of the rare-earth metals.
- It oxidizes rapidly when exposed to air.
- Cold water attacks lanthanum slowly, and hot water attacks it much more rapidly.
- The metal reacts directly with elemental carbon, nitrogen, boron, selenium, silicon, phosphorus, sulphur, and with halogens.
- Lanthanum metal is available commercially so it is not normally necessary to make it in the laboratory, which is just as well as it is difficult to separate it from pure metal.
- This is largely because of the way it is found in nature.
- The lanthanoids are found in nature in a number of minerals.
- The most important are xenotime, monazite, and bastnaesite.
- The most common lanthanoids in these minerals are, cerium, lanthanum, neodymium, and praseodymium.
- Monazite also contains thorium and ytrrium which makes handling difficult since thorium and its decomposition products are radioactive.
- For many purposes it is not particularly necessary to separate the metals, but if separation into individual metals is required, the process is complex.
- Initially, the metals are extracted as salts from the ores by extraction with sulphuric acid, hydrochloric acid, and sodium hydroxide.
- It is a component of misch metal, which is used as cigarette-lighter flints, as a deoxidizer in electron tubes, and in metallurgy.
- The oxide is a component of special glasses used in photographic lenses.
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Information about other elements may be seen at this Chemical Elements List.
A special unit about words that include chemo-, chem- may be seen here.