| Revision as of 16:57, 7 December 2005 editPyrococcal (talk | contribs)Extended confirmed users5,494 editsNo edit summary← Previous edit | Revision as of 16:57, 7 December 2005 edit undoPyrococcal (talk | contribs)Extended confirmed users5,494 editsmNo edit summaryNext edit → | ||
| Line 1: | Line 1: | ||
| ] | ] | ||
| '''Rare earth elements''' or '''rare earth metals''' are trivial names sometimes applied to a collection of 17 ]s (see ]), namely ], ], and the ]s. The |
'''Rare earth elements''' or '''rare earth metals''' are trivial names sometimes applied to a collection of 17 ]s (see ]), namely ], ], and the ]s. The term "rare earth" is deprecated by ], as these elements are not particularly 'rare', but are actually relatively abundant in the Earth's crust compared with commonly used metals such as tin and lead. (The lanthanide ], which does not occur naturally on Earth, is not generally not considered a rare earth element.) | ||
| The rare earth elements are named after their oxides, the ]s. At the time of their discovery, these were difficult to extract from the rocks that contained them and thought to be scarce. Sometimes the rare earth elements themselves are referred to as 'rare earths'. | The rare earth elements are named after their oxides, the ]s. At the time of their discovery, these were difficult to extract from the rocks that contained them and thought to be scarce. Sometimes the rare earth elements themselves are referred to as 'rare earths'. | ||
Revision as of 16:57, 7 December 2005
Rare earth elements or rare earth metals are trivial names sometimes applied to a collection of 17 chemical elements (see Periodic Table), namely scandium, yttrium, and the lanthanides. The term "rare earth" is deprecated by IUPAC, as these elements are not particularly 'rare', but are actually relatively abundant in the Earth's crust compared with commonly used metals such as tin and lead. (The lanthanide promethium, which does not occur naturally on Earth, is not generally not considered a rare earth element.)
The rare earth elements are named after their oxides, the rare earths. At the time of their discovery, these were difficult to extract from the rocks that contained them and thought to be scarce. Sometimes the rare earth elements themselves are referred to as 'rare earths'.
The elemental forms of rare earths are iron gray to silvery lustrous metals that are typically soft, malleable, and ductile and usually reactive, especially at elevated temperatures or when finely divided. All rare earth elements dissolve in acid to form triply charged ions in solution, and +3 is the default oxidation state.
The rare earths' unique properties are used in a wide variety of applications. For example, their ions are widely used as dopants in active laser media such as Nd:YAG (neodymium-doped yttrium aluminum garnet) and Erbium-doped fiber amplifiers. Half-full f shells in these elements can be used to produce exceedingly strong permanent magnets, with Samarium-Cobalt holding the record for highest Curie temperature and Neodymium-Iron-Boron having the highest known permanent magnetization of any material.
The principal economic sources of rare earths are the minerals bastnasite, monazite, and loparite and the lateritic ion-adsorption clays. The moniker "rare earth" can be misleading – the elements range in crustal abundance from cerium, the 25th most abundant element of the 78 common elements in the Earth's crust at 60 parts per million (more common than lead), to thulium and lutetium, the least abundant rare-earth elements at about 0.5 parts per million.
 | This chemistry-related article is a stub. You can help Misplaced Pages by expanding it. |