Lanthanum 17744 225683050 2008-07-14T21:52:02Z Arkuat 29003 /* Characteristics */ section title according to wikiproject elements {{Elementbox_header | number=57 | symbol=La | name=lanthanum | left=[[barium]] | right=[[cerium]] | above=- | below=[[actinium|Ac]] | color1=#ffbfff | color2=black }} {{Elementbox_series | [[lanthanide]]s }} {{Elementbox_groupperiodblock | group=3 | period=6 | block=f }} {{Elementbox_appearance_img | La,57| silvery white }} {{Elementbox_atomicmass_gpm | [[1 E-25 kg|138.90547]][[List of elements by atomic mass|(7)]] }} {{Elementbox_econfig | &#91;[[xenon|Xe]]&#93; 5d<sup>1</sup> 6s<sup>2</sup> }} {{Elementbox_epershell | 2, 8, 18, 18, 9, 2 }} {{Elementbox_section_physicalprop | color1=#ffbfff | color2=black }} {{Elementbox_phase | [[solid]] }} {{Elementbox_density_gpcm3nrt | 6.162 }} {{Elementbox_densityliq_gpcm3mp | 5.94 }} {{Elementbox_meltingpoint | k=1193 | c=920 | f=1688 }} {{Elementbox_boilingpoint | k=3737 | c=3464 | f=6267 }} {{Elementbox_heatfusion_kjpmol | 6.20 }} {{Elementbox_heatvaporiz_kjpmol | 402.1 }} {{Elementbox_heatcapacity_jpmolkat25 | 27.11 }} {{Elementbox_vaporpressure_katpa | 2005 | 2208 | 2458 | 2772 | 3178 | 3726 | comment=(extrapolated) }} {{Elementbox_section_atomicprop | color1=#ffbfff | color2=black }} {{Elementbox_crystalstruct | hexagonal }} {{Elementbox_oxistates | 3<br />(strongly [[base (chemistry)|basic]] oxide) }} {{Elementbox_electroneg_pauling | 1.10 }} {{Elementbox_ionizationenergies4 | 538.1 | 1067 | 1850.3 }} {{Elementbox_atomicradius_pm | [[1 E-10 m|195]] }} {{Elementbox_covalentradius_pm | [[1 E-10 m|169]] }} {{Elementbox_section_miscellaneous | color1=#ffbfff | color2=black }} {{Elementbox_magnetic | ? }} {{Elementbox_eresist_ohmm | ([[room temperature|r.t.]]) (α, poly) 615 n}} {{Elementbox_thermalcond_wpmkat300k | 13.4 }} {{Elementbox_thermalexpansion_umpmk | ([[room temperature|r.t.]]) (α, poly)<br />12.1 }} {{Elementbox_speedofsound_rodmpsat20 | 2475 }} {{Elementbox_youngsmodulus_gpa | (α form) 36.6 }} {{Elementbox_shearmodulus_gpa | (α form) 14.3 }} {{Elementbox_bulkmodulus_gpa | (α form) 27.9 }} {{Elementbox_poissonratio | (α form) 0.280 }} {{Elementbox_mohshardness | 2.5 }} {{Elementbox_vickershardness_mpa | 491 }} {{Elementbox_brinellhardness_mpa | 363 }} {{Elementbox_cas_number | 7439-91-0 }} {{Elementbox_isotopes_begin | color1=#ffbfff | color2=black }} {{Elementbox_isotopes_decay | mn=137 | sym=La | na=[[synthetic radioisotope|syn]] | hl=[[1 E s|60,000 yrs]] | dm=[[electron capture|ε]] | de=0.600 | pn=137 | ps=[[barium|Ba]] }} {{Elementbox_isotopes_decay2 | mn=138 | sym=La | na=0.09% | hl=[[1 E s|1.05&times;10<sup>11</sup>yrs]] | dm1=[[electron capture|ε]] | de1=1.737 | pn1=138 | ps1=[[barium|Ba]] | dm2=[[beta emission|β<sup>-</sup>]] | de2=1.044 | pn2=138 | ps2=[[cerium|Ce]] }} {{Elementbox_isotopes_stable | mn=139 | sym=La | na=99.91% | n=82 }} {{Elementbox_isotopes_end}} {{Elementbox_footer | color1=#ffbfff | color2=black }} '''Lanthanum''' ({{pronEng|ˈlænθənəm}}) is a [[chemical element]] with the symbol '''La''' and [[atomic number]] 57. == Characteristics == [[Image:Lanthan 1.jpg|left|thumb|100px|Lanthanum.]] Lanthanum is a silvery white metallic element that belongs to group 3 of the periodic table and is a [[lanthanide]]. Found in some rare-earth minerals, usually in combination with [[cerium]] and other [[rare earth element]]s. Lanthanum is malleable, ductile, and soft enough to be cut with a knife. It is one of the most reactive of the rare-earth metals. The metal reacts directly with elemental [[carbon]], [[nitrogen]], [[boron]], [[selenium]], [[silicon]], [[phosphorus]], [[sulfur]], and with [[halogen]]s. It oxidizes rapidly when exposed to air. Cold water attacks lanthanum slowly, while hot water attacks it much more rapidly. == Applications == Uses of lanthanum: * Carbon [[lighting]] applications, especially by the [[film|motion picture]] industry for studio lighting and projection. * [[Lanthanum oxide|La<sub>2</sub>O<sub>3</sub>]] improves the alkali resistance of [[glass]], and is used in making special optical glasses, such as: ** [[Infrared]] absorbing glass. ** [[Camera]] and [[telescope]] [[Lens (optics)|lenses]], because of the high [[refractive index]] and low dispersion of rare-earth glasses. * Small amounts of lanthanum added to [[steel]] improves its [[malleability]], resistance to impact and [[ductility]]. * Small amounts of lanthanum added to [[iron]] helps to produce nodular [[pig iron|cast iron]]. * Small amounts of lanthanum added to [[molybdenum]] decreases the hardness of this metal and its sensitivity to temperature variations. * Small amounts of lanthanum are present in many pool products to remove the phosphates that feed algae. * [[Mischmetal]], a [[pyrophoric]] alloy used e.g. in lighter flints, contains 25% to 45% lanthanum. * [[Lanthanum oxide]] and the [[lanthanum hexaboride|boride]] are used in electronic [[vacuum tube]]s as [[hot cathode]] materials with strong emissivity of [[electron]]s. Crystals of [[lanthanum hexaboride|LaB<sub>6</sub>]] are used in high brightness, extended life, thermionic electron emission sources for [[scanning electron microscope]]s. * in [[Gas tungsten arc welding]] electrodes, as a substitute for [[radioactive]] [[thorium]]. * [[Hydrogen sponge alloy]]s can contain lanthanum. These alloys are capable of storing up to 400 times their own volume of hydrogen gas in a reversible adsorption process. * [[Petroleum cracking]] [[catalyst]]s. * Gas lantern [[gas mantle|mantles]]. * Glass and lapidary polishing compound. * [[lanthanum-barium dating|La-Ba]] age [[radiometric dating|dating]] of rocks and ores. * [[Lanthanum carbonate]] is used medically as a [[phosphate binder]] for the treatment of [[hyperphosphatemia]]. See details below under '''Biological Role'''. * [[Lanthanum nitrate]] is mainly applied in specialty glass, water treatment and catalyst. * [[Cerium]] activated [[Lanthanum bromide]] is the recent inorganic [[scintillator]] which has a combination of high light yield and the best energy resolution. * [[Lanthanum fluoride]] is used with [[Europium flouride]] in the [[crystal membrane]] of Fluoride [[Ion-Selective Electrodes]] * [[Lanthanum Oxide]] is used as a grain growth additive during the liquid phase sintering of [[silicon nitride]]. * Like [[horseradish peroxidase]], lanthanum is used as an electron-dense tracer in [[molecular biology]]<ref>{{cite journal | author=Chau YP, Lu KS | title=Investigation of the blood-ganglion barrier properties in rat sympathetic ganglia by using lanthanum ion and horseradish peroxidase as tracers | journal=Acta Anatomica (Basel) | volume=153 | issue=2 | year=1995 | pages=135–144 | pmid=8560966 }}</ref>. == History == Lanthanum was discovered in [[1839]] by [[Swedish people|Swedish]] [[chemist]] [[Carl Gustav Mosander]], when he partially decomposed a sample of cerium nitrate by heating and treating the resulting salt with dilute [[nitric acid]]. From the resulting solution, he isolated a new rare earth he called ''lantana''. Lanthanum was isolated in relatively pure form in [[1923]]. The word ''lanthanum'' comes from the Greek ''λανθανω'' [lanthanō] = to lie hidden. Lanthanum is the most strongly basic of all the trivalent lanthanides, and this property is what allowed Mosander to isolate and purify the salts of this element. Basicity separation as operated commercially involved the fractional precipitation of the weaker bases (such as [[didymium]]) from nitrate solution by the addition of magnesium oxide or dilute ammonia gas. Purified lanthanum remained in solution. (The basicity methods were only suitable for lanthanum purification; didymium could not be efficiently further separated in this manner.) The alternative technique of fractional crystallization was invented by Dimitry Mendeleev himself, in the form of the double ammonium nitrate tetrahydrate, which he used to separate the less-soluble lanthanum from the more-soluble didymium in the 1870s. This system would be used commercially in lanthanum purification until the development of practical solvent extraction methods that started in the late 1950s. (A detailed process using the double ammonium nitrates to provide 4N pure lanthanum, neodymium concentrates and praseodymium concentrates is presented in Callow 1967, at a time when the process was just becoming obsolete.) As operated for lanthanum purification, the double ammonium nitrates were recrystallized from water. When later adapted by [[Carl Auer von Welsbach]] for the splitting of didymium, nitric acid was used as solvent to lower the solubility of the system. Lanthanum is relatively easy to purify, since it has only one adjacent lanthanide, cerium, which itself is very readily removed due to its potential tetravalency. == Biological role == Lanthanum has no known biological role. The element is not absorbed orally, and when injected its elimination is very slow. [[Lanthanum carbonate]] was approved as a medication (Fosrenol, [[Shire Pharmaceuticals]]) to absorb excess [[phosphate]] in cases of end-stage renal failure. Some rare-earth chlorides, such as lanthanum chloride (LaCl<sub>3</sub>), are known to have [[anticoagulant]] properties. While Lanthanum has pharmacological effects on several receptors and ion channels, its specificity for the GABA receptor is unique among divalent cations. Lanthanum acts at the same modulatory site on the GABAR as zinc- a known negative allosteric modulator. The Lanthanum cation La<sup>3+</sup> is a positive allosteric modulator at native and recombinant GABA receptors, increasing open channel time and decreasing desensitization in a subunit configuration dependent manner. == Occurrence == Although lanthanum belongs to chemical elements group called [[rare earth metals]], it is not rare at all. Lanthanum is available in relatively large quantities (32 ppm in Earth’s crust). "Rare earths" got their name since they were indeed rare as compared to the "common" earths such as lime or magnesia, and historically only a few deposits were known. [[Monazite]] (Ce, La, Th, Nd, Y)PO<sub>4</sub>, and [[bastnäsite]] (Ce, La, Y)CO<sub>3</sub>F, are the principal ores in which lanthanum occurs, in percentages of up to 25 to 38 percent of the total lanthanide content. Lanthanum is more generally enriched in bastnäsite as opposed to monazite, in commercial orebodies. Until 1949, bastnäsite was a rare and obscure mineral, not even remotely contemplated as a potential commercial source for lanthanides. In that year, the vast deposit at [[Mountain Pass, California]] was discovered. This discovery alerted geologists as to the existence of a whole new class of rare earth deposit, the rare-earth bearing carbonatite, other examples of which soon surfaced, particularly in Africa and China. ''See also [[:category:Lanthanide minerals]]'' == Isotopes == {{main|isotopes of lanthanum}} Naturally occurring lanthanum is composed of one stable (<sup>139</sup>La) and one [[radioactive]] (<sup>138</sup>La) [[isotope]], with the stable isotope, <sup>139</sup>La, being the most abundant (99.91% [[natural abundance]]). 38 [[radioisotope]]s have been characterized with the most stable being <sup>138</sup>La with a [[half-life]] of 105&times;10<sup>9</sup> years, and <sup>137</sup>La with a half-life of 60,000 years. Most of the remaining radioactive isotopes have half-lives that are less than 24 hours and the majority of these have half lives that are less than 1 minute. This element also has 3 [[meta state]]s. The isotopes of lanthanum range in [[atomic weight]] from 117 [[atomic mass unit|u]] (<sup>117</sup>La) to 155 u (<sup>155</sup>La). == Precautions == Lanthanum has a low to moderate level of toxicity, and should be handled with care. In animals, the injection of lanthanum solutions produces [[glycaemia]], low blood pressure, degeneration of the [[spleen]] and [[liver|hepatic]] alterations. ==References== {{reflist}} *[http://periodic.lanl.gov/elements/57.html Los Alamos National Laboratory &ndash; Lanthanum] * "The Industrial Chemistry of the Lanthanons, Yttrium, Thorium and Uranium", by R.J. Callow, Pergamon Press 1967 * "Chemistry of the Lanthanons", by R.C. Vickery, Butterworths 1953 * "Nouveau Traite de Chimie Minerale, Vol. VII. Scandium, Yttrium, Elements des Terres Rares, Actinium", P. Pascal, Editor, Masson & Cie 1959 * "Extractive Metallurgy of Rare Earths", by C.K. Gupta and N. Krishnamurthy, CRC Press 2005 ==See also== [[:Category:Lanthanum compounds| Lanthanum compounds]] == External links == {{Commons|Lanthanum}} {{wiktionary|lanthanum}} *[http://www.webelements.com/webelements/elements/text/La/index.html WebElements.com &ndash; Lanthanum] {{clear}} {{Compact periodic table}} [[Category:Chemical elements]] [[Category:Lanthanides]] <!-- interwiki --> [[af:Lantaan]] [[ar:لانثانوم]] [[bn:ল্যান্থানাম]] [[be:Лантан]] [[bs:Lantan]] [[ca:Lantani]] [[cv:Лантан]] [[cs:Lanthan]] [[co:Lantaniu]] [[da:Lanthan]] [[de:Lanthan]] [[et:Lantaan]] [[el:Λανθάνιο]] [[es:Lantano]] [[eo:Lantano]] [[eu:Lantano]] [[fr:Lanthane]] [[fur:Lantani]] [[gv:Lantanum]] [[gl:Lantano]] [[ko:란타넘]] [[hy:Լանթան]] [[hr:Lantan]] [[io:Lantano]] [[id:Lantanum]] [[it:Lantanio]] [[he:לנתן]] [[jv:Lantanum]] [[ht:Lantàn]] [[la:Lanthanum]] [[lv:Lantāns]] [[lb:Lanthan]] [[lt:Lantanas]] [[jbo:jinmrlantano]] [[hu:Lantán]] [[ml:ലാന്തനം]] [[nl:Lanthanium]] [[ja:ランタン]] [[no:Lantan]] [[nn:Lantan]] [[oc:Lantani]] [[pl:Lantan]] [[pt:Lantânio]] [[ro:Lantan]] [[qu:Lanthanu]] [[ru:Лантан]] [[scn:Lantaniu]] [[simple:Lanthanum]] [[sk:Lantán]] [[sl:Lantan]] [[sr:Лантан]] [[sh:Lantan]] [[fi:Lantaani]] [[sv:Lantan]] [[ta:லாந்த்தனம்]] [[th:แลนทานัม]] [[vi:Lantan]] [[tr:Lantan]] [[uk:Лантан]] [[zh:镧]]