rare-earth element

(râr′ûrth′)n. Any of a group of 17 naturally occurring metallic elements that have similar properties, consisting of scandium, yttrium, and the 15 elements with atomic numbers 57 through 71 (the lanthanides). The rare-earth elements are widely used in electronics and other high-tech products.

[rare earth.]

rare′-earth′ el`ement

n. any of a group of closely related metallic elements, comprising the lanthanides, scandium, and yttrium, that are chemically similar in having the same number of valence electrons. Also called rare′-earth′ met`al. [1955–60]

rare-earth element

(râr′ûrth′) See lanthanide.

Thesaurus

Noun

rare-earth element - any element of the lanthanide series (atomic numbers 57 through 71)lanthanide, lanthanoid, lanthanon, rare earthgroup, grouping - any number of entities (members) considered as a unitterbium metal - a separate group of related lanthanides, including terbium, europium, gadolinium, and sometimes dysprosium

Rare-Earth Element

rare-earth element

[′rer ‚ərth ′el·ə·mənt] (chemistry) The name given to any of the group of chemical elements with atomic numbers 58 to 71; the name is a misnomer since they are neither rare nor earths; examples are cerium, erbium, and gadolinium.

Rare-Earth Element

any one of a group of chemical elements belonging to a secondary subgroup of group III of Mendeleev’s periodic system. The elements are scandium (symbol Sc, atomic number [Z] = 21), yttrium (Y, Z = 39), lanthanum (La, Z = 57), and the lanthanides (14 elements wherein Z ranges from 58 to 71). Scandium, however, is not always classed as a rare-earth element.

In the free state, rare-earth elements are metals. The term “rare-earth” was assigned to these elements because they occur relatively rarely in the earth’s crust and because they form refractory oxides that are practically insoluble in water. Prior to and during the early 19th century, such oxides were called common earths. An important characteristic of rare-earth elements is their occurrence together in nature. For example, the mineral monazite, one of the primary sources of these elements, contains phosphates of Y, La, and other rare earths. All rare earths display similar chemical properties; their characteristic oxidation state is +3 (valence of three). In the Sc-Y-La series, the basic properties of oxides and hydroxides become more pronounced from Sc to La. For example, scandium hydroxide Sc(OH)₃ is amphoteric, whereas lanthanum hydroxide La(OH)₃ is a rather strong base.

Actinium (Z = 89) closely resembles the rare-earth elements in chemical properties, but it is generally regarded separately because of its radioactivity (lack of stable isotopes).

S. S. BERDONOSOV

rare-earth element

rare-earth element

rare′-earth′ el`ement

rare-earth element

Rare-Earth Element

rare-earth element

Rare-Earth Element

rare-earth element

Synonyms for rare-earth element

noun any element of the lanthanide series (atomic numbers 57 through 71)

Synonyms

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