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lanthanide Chem.|ˈlænθənaɪd|
[ad. G. lanthanid (V. M. Goldschmidt et al. 1925, in Skrifter Norske Vidensk-Akad. (Mat.-nat. Kl.) v. 6), f. lanthan lanthanum: see -ide 2.]
1. Any of the series of elements with an atomic number between 57 (lanthanum) and 71 (lutetium) inclusive, or (following the later definition by Goldschmidt et al., on the suggestion of A. Sommerfeld, in loc. cit. vii. 10), between 58 (cerium) and 71; all these elements occupy a single position in group IIIa of the periodic table, are predominantly trivalent electropositive metals with similar chemical properties, and occur together in monazite, gadolinite, and certain other minerals. Cf. rare earth.
1926Chem. Abstr. XX. 1969 (heading) Synthetic pyro⁓morphites, vanadinites and mimetites in which lead is partially substituted by lanthanides. 1937Jrnl. Chem. Soc. 662 A large rather coherent group is furnished by the rare-earth elements, comprising the lanthanide family (elements of atomic number from 57 to 71) and yttrium. 1946J. R. Partington Gen. & Inorg. Chem. x. 262 The rare-earth elements in this period (sometimes called lanthanides, to distinguish them from the total number of rare-earth elements which includes scandium and yttrium in earlier periods). 1950N. V. Sidgwick Chem. Elements I. 444 Two of the lanthanides, samarium and lutecium, have been found to be radioactive. 1957Sci. News XLV. 95 In the conventional periodic table..the pigeon-hole allotted to the element lanthanum..contains fourteen additional elements, formerly called the ‘Rare Earths’, but now usually called the ‘Lanthanons’ or ‘Lanthanides’. 1965[see F III. 1 j]. 1973J. J. Lagowski Mod. Inorg. Chem. xvi. 616 The trivalent lanthanide cations also exhibit striking colors in their crystalline salts and in aqueous solution. 1973Chem. Soc. Rev. II. 49 The most common practice is to successively add known amounts of the lanthanide shift reagent..to the compound under study..and record the n.m.r. spectrum after each addition.
2. Comb.: lanthanide contraction [tr. G. lanthanidenkontraktion (V. M. Goldschmidt et al. 1925, in Skrifter Norske Vidensk.-Akad. (Mat.-nat. Kl.) vii. 13)], the decrease in atomic and ionic radii with increasing atomic number observed in the lanthanide series; lanthanide series, the series of elements from lanthanum (or cerium) to lutetium.
1926Chem. Abstr. XX. 131 ‘Lanthanide contraction’ is the term applied to the volume contraction of the atoms in the rare earth series Ce–Cu [sic]. This contraction opposes the progressive increase of at. vol. in each vertical column of the periodic table. 1945A. F. Wells Structural Inorg. Chem. iii. 94 As a result of this ‘lanthanide contraction’, so called because it is observed in the elements following lanthanum, certain pairs of elements in the same Periodic Group have practically identical ionic (and atomic) radii. 1971Jrnl. Inorg. & Nucl. Chem. XXXIII. 385 The lanthanide contraction as reflected in certain properties of the lanthanide compounds is not a smooth function of Z.
1945,1958Lanthanide series [see actinide]. 1965B. G. Wybourne Spectroscopic Properties Rare Earths i. 2 As we proceed through the lanthanide series, the nuclear charge, together with the number of 4f-electrons, increases by one at each step. |