terbium

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terbium

(tûr`bēəm) [from Ytterby, a village in Sweden], metallic chemical element; symbol Tb; at. no. 65; at. wt. 158.92535; m.p. 1,356°C;; b.p. 3,123°C;; sp. gr. about 8.25; valence +3 or +4. Terbium is a soft, malleable, ductile, silver-gray metal. It is one of the rare-earth metalsrare-earth metals,
in chemistry, group of metals including those of the lanthanide series and actinide series and usually yttrium, sometimes scandium and thorium, and rarely zirconium. Promethium, which is not found in nature, is not usually considered a rare-earth metal.
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 of the lanthanide serieslanthanide series,
a series of metallic elements, included in the rare-earth metals, in Group 3 of the periodic table. Members of the series are often called lanthanides, although lanthanum (atomic number 57) is not always considered a member of the series.
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 in Group 3 of the periodic tableperiodic table,
chart of the elements arranged according to the periodic law discovered by Dmitri I. Mendeleev and revised by Henry G. J. Moseley. In the periodic table the elements are arranged in columns and rows according to increasing atomic number (see the table entitled
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. It does not tarnish rapidly in air. Its oxide, terbia, Tb2O3, is white; its peroxide, Tb4O7, is dark brown to black. Most of the salts are colorless or white and all contain trivalent terbium. The element and its compounds have limited commercial importance; some minor uses are in lasers, semiconductor devices, and phosphors for color television picture tubes. Terbium is found in gadolinite, cerite, and other rare-earth minerals and is recovered from euxenite, monazite, and zenotime. It is difficult to separate it from the other rare-earth metals; several methods are used. The pure metal may be produced by chemical reduction of the halide with calcium. The element was discovered in 1843 by C. G. Mosander as its oxide, which he called erbia. The element has been known as terbium since 1877.

Terbium

 

Tb, the chemical element with atomic number 65 and atomic weight 158.9254; a rare-earth metal and a lanthanide.

terbium

[′tər·bē·əm]
(chemistry)
A rare-earth element, symbol Tb, in the yttrium subgroup of the transition elements, atomic number 65, atomic weight 158.9254.

terbium

a soft malleable silvery-grey element of the lanthanide series of metals, occurring in gadolinite and monazite and used in lasers and for doping solid-state devices. Symbol: Tb; atomic no.: 65; atomic wt.: 158.92534; valency: 3 or 4; relative density: 8.230; melting pt.: 1356°C; boiling pt.: 3230°C