lanthanum


Also found in: Dictionary, Thesaurus, Medical, Financial, Acronyms, Wikipedia.
Related to lanthanum: Lanthanum oxide, Lanthanum carbonate

lanthanum

(lăn`thənəm) [Gr.,=to lie hidden], metallic chemical element; symbol La; at. no. 57; at. wt. 138.90547; m.p. about 920°C;; b.p. about 3,460°C;; sp. gr. 6.19 at 25°C;; valence +3. Lanthanum is a soft, malleable, ductile, silver-white metal; at room temperature it has a hexagonal close-packed crystalline structure that is unstable at higher temperatures (see allotropyallotropy
[Gr.,=other form]. A chemical element is said to exhibit allotropy when it occurs in two or more forms in the same physical state; the forms are called allotropes.
..... Click the link for more information.
). Lanthanum is usually considered the first member 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.
..... Click the link for more information.
, a group of elements with similar physical and chemical properties. 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.
..... Click the link for more information.
 of 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.
. Lanthanum is a chemically active element. It oxidizes rapidly in air and reacts with water to form the hydroxide. It reacts readily with acids, with elemental boron, carbon, nitrogen, phosphorus, selenium, silicon, or sulfur, and with the halogens. The oxide and the boride are used in electronic vacuum tubes; the oxide is added to optical glass to increase its alkali resistance and refractive index. Its aluminate is a perovskite ceramic used as a superconductor substrate. Although lanthanum is not found uncombined in nature, it occurs in the rare-earth minerals monazitemonazite
, yellow to reddish-brown natural phosphate of the rare earths, mainly the cerium and lanthanum metals, usually with some thorium. Yttrium, calcium, iron, and silica are frequently present.
..... Click the link for more information.
 and bastnasite. Lanthanum may be prepared by reduction of lanthanum fluoride with calcium metal. Lanthanum is used in rechargeable nickel-metal hydride batteries. It may be used in making ductile cast ironiron,
metallic chemical element; symbol Fe [Lat. ferrum]; at. no. 26; at. wt. 55.845; m.p. about 1,535°C;; b.p. about 2,750°C;; sp. gr. 7.87 at 20°C;; valence +2, +3, +4, or +6. Iron is biologically significant.
..... Click the link for more information.
; alloyed with other metals, it is used in cigarette lighter flints. Natural lanthanum is a mixture of two stable isotopes. One radioactive byproduct of the fission of plutonium, thorium, or uranium is a mixture of radioactive isotopes of lanthanum; 17 radioactive isotopes are known. Lanthanum was discovered in the form lanthanium oxide, called lanthana, in 1839 by C. G. Mosander.

lanthanum

[′lan·thə·nəm]
(chemistry)
A chemical element, symbol La, atomic number 57, atomic weight 138.91; it is the second most abundant element in the rare-earth group.
(metallurgy)
A white, soft, malleable metal; tarnishes in moist air; a major component of misch metal.

lanthanum

a silvery-white ductile metallic element of the lanthanide series, occurring principally in bastnaesite and monazite: used in pyrophoric alloys, electronic devices, and in glass manufacture. Symbol: La; atomic no.: 57; atomic wt.: 138.9055; valency: 3; relative density: 6.145; melting pt.: 918?C; boiling pt.: 3464?C
References in periodicals archive ?
Eight hundred hemodialysis patients were randomized to either lanthanum or calcium carbonate and treated for six months.
Similarly, after 12 weeks of treatment with lanthanum carbonate, the co-occurrence network of microbial genera in patients was simplified when compared with that without treatment [Figure 5].{Figure 5}{Figure 6}
Among the rare earths are lanthanum, cerium, neodymium, terbium, and dysprosium.
Generally, in the samples treated for shorter times the darker zones rich in pores were more visible and in many areas lanthanum layer is irregular and thinner than the ones treated for 30 min.
SEM of LDPOG gives the changes in morphology of the Pyrolusite after lanthanum was doped and was shown in Figure 1(b).
Is granular formulation of lanthanum carbonate more effective than chewable tablets?
Lanthanum doped bismuth iron oxide thin films were prepared using sol-gel method.
Lanthanum and cerium will be removed from the rare earth chloride solution using solvent extraction to produce four different rare earth products: lanthanum oxide, 99% grade; cerium hydroxide, 99% grade; mixed lanthanum and cerium oxide, 99% grade; and mixed praseodymium and lutetium oxide.
In one example, nanofillers of carbon black and lanthanum hexaboride are used.
Portable, handheld radioisotope identification instrument (RIID) technology typically uses one of two types of detector material--sodium iodide (NaI) or lanthanum bromide (LaBr)--in combination with a multi-channel analyzer to segregate pulses from specific gamma energies, that provides a gamma-energy spectrum used to identify a specific radioisotope.
The rest of the volume is devoted to paragraph-long abstracts of articles on properties of lanthanum hexaboride.