lanthanide series

lanthanide series,

a series of metallic elements, included in 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.
..... Click the link for more information. , 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
..... Click the link for more information. . Members of the series are often called lanthanides, although lanthanumlanthanum
[Gr.,=to lie hidden], metallic chemical element; symbol La; at. no. 57; at. wt. 138.90547; m.p. about 920&degC;; b.p. about 3,460&degC;; sp. gr. 6.19 at 25&degC;; valence +3.
..... Click the link for more information. (atomic number 57) is not always considered a member of the series. The series always includes the 14 elements with atomic numbers 58 through 71, which are (in order of increasing atomic number) ceriumcerium
[from the asteroid Ceres], metallic chemical element; symbol Ce; at. no. 58; at. wt. 140.116; m.p. 799&degC;; b.p. 3,426&degC;; sp. gr. 6.77 at 25&degC;; valence +3 or +4. Cerium is a soft, malleable, ductile, iron-grey metal with hexagonal or cubic crystalline structure.
..... Click the link for more information. , praseodymiumpraseodymium
[Gr., =green twin], metallic chemical element; symbol Pr; at. no. 59; at. wt. 140.90765; m.p. 931&degC;; b.p. 3,512&degC;; sp. gr. about 6.8; valence +3 or +4. Praseodymium is a soft, malleable, ductile, silver-yellow metal.
..... Click the link for more information. , neodymiumneodymium
, metallic chemical element; symbol Nd; at. no. 60; at. wt. 144.242; m.p. about 1,021&degC;; b.p. about 3,068&degC;; sp. gr. 7.004 at 20&degC;; valence +3. Neodymium is a lustrous silver-yellow metal.
..... Click the link for more information. , promethiumpromethium
, artificially produced radioactive chemical element; symbol Pm; at. no. 61; mass no. of most stable isotope 145; m.p. 1,042&degC;; b.p. 3,000&degC; (estimated); sp. gr. unknown; valence +3.
..... Click the link for more information. , samariumsamarium
, metallic chemical element; symbol Sm; at. no. 62; at. wt. 150.36; m.p. 1,072&degC;; b.p. 1,791&degC;; sp. gr. 7.54 at 20&degC;; valence +2 or +3. Samarium is a lustrous silver-white metal.
..... Click the link for more information. , europiumeuropium
[from Europe], metallic chemical element; symbol Eu; at. no. 63; at. wt. 151.964; m.p. about 820&degC;; b.p. about 1,600&degC;; sp. gr. 5.25 at 25&degC;; valence +2 or +3. Europium is a ductile silvery-white metal; it is both rare and expensive.
..... Click the link for more information. , gadoliniumgadolinium
, metallic chemical element; symbol Gd; at. no. 64; at. wt. 157.25; m.p. 1,312&degC;; b.p. 3,233&degC;; sp. gr. 7.898 at 25&degC;; valence +3. Gadolinium is a malleable, ductile, lustrous silver-white metal with a hexagonal close-packed crystalline structure at room
..... Click the link for more information. , terbiumterbium
[from Ytterby, a village in Sweden], metallic chemical element; symbol Tb; at. no. 65; at. wt. 158.92535; m.p. 1,356&degC;; b.p. 3,123&degC;; sp. gr. about 8.25; valence +3 or +4. Terbium is a soft, malleable, ductile, silver-gray metal.
..... Click the link for more information. , dysprosiumdysprosium
[Gr.,=hard to get at], metallic chemical element; symbol Dy; at. no. 66; at. wt. 162.500; m.p. 1,412&degC;; b.p. 2,562&degC;; sp. gr. 8.54 at 25&degC;; valence+3. Dysprosium is a lustrous silvery metal; it is very soft and can be cut with a knife.
..... Click the link for more information. , holmiumholmium
[Lat.,=Stockholm], metallic chemical element; symbol Ho; at. no. 67; at. wt. 164.93032; m.p. about 1,474&degC;; b.p. about 2,425&degC;; sp. gr. 8.78 at 25&degC;; valence +3.
..... Click the link for more information. , erbiumerbium
[from Ytterby, a town in Sweden], metallic chemical element; symbol Er; at. no. 68; at. wt. 167.259; m.p. 1,529&degC;; b.p. 2,863&degC;; sp. gr. 9.05 at 25&degC;; valence +3. Erbium is a soft, malleable, lustrous, silvery metal.
..... Click the link for more information. , thuliumthulium
[from Thule, an ancient name for Scandinavia], metallic chemical element; symbol Tm; at. no. 69; at. wt. 168.93421; m.p. about 1,545&degC;; b.p. 1,947&degC;; sp. gr. 9.3; valence +3. Thulium is a soft, malleable, ductile, lustrous silver-white metal.
..... Click the link for more information. , ytterbiumytterbium
[for Ytterby, a town in Sweden], metallic chemical element; symbol Yb; at. no. 70; at. wt. 173.054; m.p. 819&degC;; b.p. about 1,194&degC;; sp. gr. about 7.0; valence +2 or +3. Ytterbium is a soft, malleable, ductile, lustrous silver-white metal.
..... Click the link for more information. , and lutetiumlutetium,
formerly lutecium
, metallic chemical element; symbol Lu; atomic number 71; at. wt. 174.9668; m.p. about 1,663&degC;; b.p. about 3,395&degC;; sp. gr. 9.835 at 25&degC;; valence +3. Lutetium is a silver-white metal that is relatively stable in air.
..... Click the link for more information. . All of the members of the series very closely resemble lanthanum and one another in their chemical and physical properties; as the atomic number increases in this series, added electrons enter the 4f electron orbital. Chemically, they are about as reactive as calcium. They all form trivalent compounds; some also form divalent or tetravalent compounds. The lanthanides have similiar sizes so that any given compound of the rare earths is likely to crystallize with the same structure as any other rare earth; however, the lattice parameters become smaller and the crystal denser as compounds proceed across the series.