Lanthanum

Lanthanum is a chemical element with the symbol La and atomic number 57. It is a soft, ductile, silvery-white metal that tarnishes slowly when exposed to air and is soft enough to be cut with a knife. It is the eponym of the lanthanide series, a group of 15 similar elements between lanthanum and lutetium in the periodic table, of which lanthanum is the first and the prototype. Lanthanum is traditionally counted among the rare earth elements. The usual oxidation state is +3. Lanthanum has no biological role and is not very toxic.

History

Lanthanum was discovered by Carl Gustaf Mosander, a Swedish chemist, in 1839. Mosander was working with a sample of cerium when he discovered a new element that he named lanthanum; the name comes from the Ancient Greek λανθάνειν (lanthanein), meaning "to lie hidden". Despite its name, lanthanum has a relatively high natural abundance on Earth, more than three times as abundant as lead in the Earth's crust, for example.

Characteristics

Lanthanum is the first element and eponym of the lanthanide series. In the periodic table, it appears to the right of the alkali metal rubidium, to the left of the actinide thorium, and below the lanthanide cerium. The element is often associated with the rare earth elements and is classified as such.

Applications

Lanthanum has numerous applications. For example, small amounts of lanthanum added to steel improves its malleability, resistance to impact and ductility. Lanthanum is also used in a variety of other applications, such as in the production of catalysts which are used in petroleum refining and as a component in special types of glass.

Precautions

While lanthanum is not considered highly toxic, it should be handled with care. The element and its compounds should not be ingested, and if they are, medical attention should be sought immediately.

See also

• List of chemical elements
• Periodic table

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Lanthanum

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