Cerium 5674 225683278 2008-07-14T21:53:10Z Arkuat 29003 /* Characteristics */ section title according to wikiproject elements {{Elementbox_header | number=58 | symbol=Ce | name=cerium | left=[[lanthanum]] | right=[[praseodymium]] | above=- | below=[[thorium|Th]] | color1=#ffbfff | color2=black }} {{Elementbox_series | [[lanthanide]]s }} {{Elementbox_periodblock | period=6 | block=f }} {{Elementbox_appearance_img | Ce,58| silvery white }} {{Elementbox_atomicmass_gpm | 140.116[[List of elements by atomic mass|(1)]] }} {{Elementbox_econfig | &#91;[[xenon|Xe]]&#93; 4f<sup>1</sup>5d<sup>1</sup>6s<sup>2</sup> }} {{Elementbox_epershell | 2, 8, 18, 19, 9, 2 }} {{Elementbox_section_physicalprop | color1=#ffbfff | color2=black }} {{Elementbox_phase | [[solid]] }} {{Elementbox_density_gpcm3nrt | 6.770 }} {{Elementbox_densityliq_gpcm3mp | 6.55 }} {{Elementbox_meltingpoint | k=1068 | c=795 | f=1463 }} {{Elementbox_boilingpoint | k=3716 | c=3443 | f=6229 }} {{Elementbox_heatfusion_kjpmol | 5.46 }} {{Elementbox_heatvaporiz_kjpmol | 398 }} {{Elementbox_heatcapacity_jpmolkat25 | 26.94 }} {{Elementbox_vaporpressure_katpa | 1992 | 2194 | 2442 | 2754 | 3159 | 3705 | comment= }} {{Elementbox_section_atomicprop | color1=#ffbfff | color2=black }} {{Elementbox_crystalstruct | cubic face centered }} {{Elementbox_oxistates | '''3''', 4<br />(mildly [[base (chemistry)|basic]] oxide) }} {{Elementbox_electroneg_pauling | 1.12 }} {{Elementbox_ionizationenergies4 | 534.4 | 1050 | 1949 }} {{Elementbox_atomicradius_pm | 185 }} {{Elementbox_section_miscellaneous | color1=#ffbfff | color2=black }} {{Elementbox_magnetic | no data }} {{Elementbox_eresist_ohmm | ([[room temperature|r.t.]]) (β, poly) 828 n}} {{Elementbox_thermalcond_wpmkat300k | 11.3 }} {{Elementbox_thermalexpansion_umpmk | ([[room temperature|r.t.]]) (γ, poly)<br />6.3 }} {{Elementbox_speedofsound_rodmpsat20 | 2100 }} {{Elementbox_youngsmodulus_gpa | (γ form) 33.6 }} {{Elementbox_shearmodulus_gpa | (γ form) 13.5 }} {{Elementbox_bulkmodulus_gpa | (γ form) 21.5 }} {{Elementbox_poissonratio | (γ form) 0.24 }} {{Elementbox_mohshardness | 2.5 }} {{Elementbox_vickershardness_mpa | 270 }} {{Elementbox_brinellhardness_mpa | 412 }} {{Elementbox_cas_number | 7440-45-1 }} {{Elementbox_isotopes_begin | color1=#ffbfff | color2=black }} {{Elementbox_isotopes_decay | mn=134 | sym=Ce | na=[[synthetic radioisotope|syn]] | hl=[[1 E s|3.16 days]] | dm=[[electron capture|ε]] | de=0.500 | pn=134 | ps=[[lanthanum|La]] }} {{Elementbox_isotopes_stable | mn=136 | sym=Ce | na=0.185% | n=78 }} {{Elementbox_isotopes_stable | mn=138 | sym=Ce | na=0.251% | n=80 }} {{Elementbox_isotopes_decay | mn=139 | sym=Ce | na=[[synthetic radioisotope|syn]] | hl=[[1 E s|137.640 days]] | dm=[[electron capture|ε]] | de=0.278 | pn=139 | ps=[[lanthanum|La]] }} {{Elementbox_isotopes_stable | mn=140 | sym=Ce | na=88.450% | n=82 }} {{Elementbox_isotopes_decay | mn=141 | sym=Ce | na=[[synthetic radioisotope|syn]] | hl=[[1 E s|32.501 days]] | dm=[[beta emission|β<sup>-</sup>]] | de=0.581 | pn=141 | ps=[[praseodymium|Pr]] }} {{Elementbox_isotopes_decay | mn=142 | sym=Ce | na=11.114% | hl=[[1 E s|> 5×10<sup>16</sup> years]] | dm=[[double beta decay|β<sup>-</sup>β<sup>-</sup>]] | de=unknown | pn=142 | ps=[[neodymium|Nd]] }} {{Elementbox_isotopes_decay | mn=144 | sym=Ce | na=[[synthetic radioisotope|syn]] | hl=[[1 E s|284.893 days]] | dm=[[beta emission|β<sup>-</sup>]] | de=0.319 | pn=144 | ps=[[praseodymium|Pr]] }} {{Elementbox_isotopes_end}} {{Elementbox_footer | color1=#ffbfff | color2=black }} '''Cerium''' ({{pronEng|ˈsɪəriəm}}) is a [[chemical element]] with the symbol '''Ce''' and [[atomic number]] 58. == Characteristics == Cerium is a silvery metal, belonging to the [[lanthanide]] group. It resembles [[iron]] in color and luster, but is soft, and both malleable and ductile. Cerium has the longest liquid range of any non-radioactive element: 2648 °C (795 °C to 3443 °C) or 4766 °F (1463 °F to 6229 °F). ([[Thorium]] has a longer liquid range.) Although cerium belongs to chemical elements group called [[rare earth metals]], it is in fact more common than [[lead]]. Cerium is available in relatively large quantities (68 ppm in Earth’s crust). It is used in some rare-earth alloys. Among rare earth elements only [[europium]] is more reactive. It tarnishes readily in the air. Alkali solutions and dilute and concentrated acids attack the metal rapidly. Cerium oxidizes slowly in cold water and rapidly in hot water. The pure metal can ignite if scratched. Cerium(IV) (ceric) salts are orange red or yellowish, whereas cerium(III) (cerous) salts are usually white or colorless. Both oxidation states absorb ultraviolet light strongly. Cerium(III) can be used to make glasses that are colorless, yet absorb ultraviolet light almost completely. Cerium can be readily detected in rare earth mixtures by a very sensitive qualitative test: addition of [[ammonia]] and [[hydrogen peroxide]] to an aqueous solution of lanthanides produces a characteristic dark brown color if cerium is present. [[Image:Img0102.jpg|Phase diagram of cerium|300px|left|thumb]] <br clear=left/> == Applications == Uses of cerium: * In [[metallurgy]]: ** Cerium is used in making [[aluminium]] [[alloy]]s. ** Adding cerium to [[cast iron]]s opposes graphitization and produces a malleable iron. ** In [[steel]]s, cerium degasifies and can help reduce sulfides and oxides. ** Cerium is used in [[stainless steel]] as a [[precipitation hardening]] agent. ** 3 to 4% cerium added to [[magnesium]] alloys, along with 0.2 to 0.6% [[zirconium]], helps [[grain refinement|refine the grain]] and give sound [[casting]] of complex shapes. It also adds heat resistance to magnesium castings. ** Cerium is used in alloys that are used to make permanent magnets. ** Cerium is used as an alloying element in [[tungsten]] electrodes for [[gas tungsten arc welding]]. ** Cerium is a major component of [[ferrocerium]], also known as "[[lighter (fire starter)|lighter]] flint". Although modern alloys of this type generally use [[Mischmetal]] rather than purified cerium, it still is the most prevalent constituent. ** Cerium is used in [[carbon arc lamp|carbon-arc lighting]], especially in the [[film|motion picture]] industry. * [[Cerium oxalate]] is an anti-emetic drug. * [[Cerium(IV) oxide]] ** The oxide is used in incandescent gas mantles, such as the [[Gas mantle|Welsbach mantle]], where it was combined with [[thorium]], [[lanthanum]], [[magnesium]] or [[yttrium]] oxides . ** The oxide is emerging as a hydrocarbon [[catalyst]] in [[self cleaning oven]]s, incorporated into oven walls. ** Cerium(IV) oxide has largely replaced [[rouge]] in the [[glass]] industry as a polishing abrasive. ** Cerium(IV) oxide is finding use as a petroleum cracking catalyst in petroleum refining. ** Cerium(IV) additives to diesel fuel cause that to burn more cleanly, with less resulting air-pollution. ** In glass, cerium(IV) oxide allows for selective absorption of [[ultraviolet light]]. * [[Cerium(IV) sulfate]] is used extensively as a volumetric [[oxidizing agent]] in quantitative analysis. * Ceric ammonium nitrate is a useful one-electron oxidant in organic chemistry, used to oxidatively etch electronic components, and as a primary standard for quantitative analysis. * Cerium compounds are used in the manufacture of [[glass]], both as a component and as a decolorizer. * Cerium in combination with titanium gives a golden yellow color to glass. * Cerium compounds are used for the coloring of enamel. * Cerium(III) and cerium(IV) compounds such as [[cerium(III) chloride]] have uses as [[catalyst]]s in [[organic synthesis]]. == History == Cerium was discovered in [[Bastnäs]] in [[Sweden]] by [[Jöns Jakob Berzelius]] and [[Wilhelm Hisinger]], and independently in [[Germany]] by [[Martin Heinrich Klaproth]], both in 1803. Cerium was so named by Berzelius after the dwarf planet {{dp|Ceres}}, discovered two years earlier (1801). As originally isolated, cerium was in the form of its oxide, and was named ''ceria'', a term that is still used. The metal itself was too electropositive to be isolated by then-current smelting technology, a characteristic of earth metals in general. However, the development of [[electrochemistry]] by [[Humphry Davy]] was only five years into the future, and then the earths were well on their way to yielding up the metals they contained. Ceria, as isolated in 1803, contained all of the lanthanides present in the cerite ore from Bastnaes, Sweden, and thus only contained about 45% of what is now known to be pure ceria. It was not until Mosander succeeded in removing lanthana and "didymia" in the late 1830s, that ceria was obtained pure. As an historical aside: Wilhelm Hisinger was a wealthy mine owner and amateur scientist, and sponsor of Berzelius. He owned or controlled the mine at Bastnaes, and had been trying for years to find out the composition of the abundant heavy gangue rock (the "Tungstein of Bastnaes"), now known as cerite, that he had in his mine. Mosander and his family lived for many years in the same house as Berzelius, and the former was undoubtedly persuaded by the latter to investigate ceria further. When the rare earths were first discovered, since they were strong bases like the oxides of calcium or magnesium, they were thought to be divalent. Thus, "ceric" cerium was thought to be trivalent, and the oxidation state ratio was therefore thought to be 1.5. Berzelius was extremely annoyed to keep on getting the ratio 1.33. He was after all one of the finest analytical chemists in Europe. But he was a better analyst than he thought, since 1.33 was the correct answer! == Occurrence == Cerium is the most abundant of the [[rare earth element]]s, making up about 0.0046% of the [[Earth's crust]] by weight. It is found in a number of minerals including [[allanite]] (also known as orthite)&mdash;(Ca, Ce, La, Y)<sub>2</sub>(Al, Fe)<sub>3</sub>(SiO<sub>4</sub>)<sub>3</sub>(OH), [[monazite]] (Ce, La, Th, Nd, Y)PO<sub>4</sub>, [[bastnasite]] (Ce, La, Y)CO<sub>3</sub>F, [[hydroxyl]][[bastnasite]] (Ce, La, Nd)CO<sub>3</sub>(OH, F), [[rhabdophane]] (Ce, La, Nd)PO<sub>4</sub>-H<sub>2</sub>O, [[zircon]] (ZrSiO<sub>4</sub>), and synchysite Ca(Ce, La, Nd, Y)(CO<sub>3</sub>)<sub>2</sub>F. Monazite and bastnasite are presently the two most important sources of cerium. Cerium is most often prepared via an [[ion exchange]] process that uses monazite sands as its cerium source. Large deposits of [[monazite]], [[allanite]], and [[bastnasite]] will supply cerium, thorium, and other rare-earth metals for many years to come. See also ''[[:Category:Lanthanide minerals]]'' == Compounds == [[Image:Cer(IV)-sulfat.JPG|200px|right|thumb|Cerium(IV)-sulfate]] Cerium has two common [[oxidation state]]s, +3 and +4. The most common compound of cerium is [[cerium(IV) oxide]] (CeO<sub>2</sub>), which is used as "jeweller's [[rouge]]" as well as in the walls of some [[self-cleaning ovens]]. Two common [[Oxidation#Oxidizing and Reducing agents|oxidising agent]]s used in [[titration]]s are [[ammonium cerium(IV) sulfate]] (ceric ammonium sulfate, (NH<sub>4</sub>)<sub>2</sub>Ce(SO<sub>4</sub>)<sub>3</sub>) and [[ammonium cerium(IV) nitrate]] (ceric ammonium nitrate or CAN, (NH<sub>4</sub>)<sub>2</sub>Ce(NO<sub>3</sub>)<sub>6</sub>). Cerium also forms a [[chloride]], CeCl<sub>3</sub> or [[cerium(III) chloride]], used to facilitate reactions at [[carbonyl group]]s in [[organic chemistry]]. Other compounds include [[cerium(III) carbonate]] (Ce<sub>2</sub>(CO<sub>3</sub>)<sub>3</sub>), [[cerium(III) fluoride]] (CeF<sub>3</sub>), [[cerium(III) oxide]] (Ce<sub>2</sub>O<sub>3</sub>), as well as [[cerium(IV) sulfate]] (ceric sulfate, Ce(SO<sub>4</sub>)<sub>2</sub>) and cerium(III) triflate (Ce(OSO<sub>2</sub>CF<sub>3</sub>)<sub>3</sub>). The two oxidation states of cerium differ enormously in basicity: cerium(III) is a strong base, comparable to the other trivalent lanthanides, but cerium(IV) is weak. This difference has always allowed cerium to be by far the most readily isolated and purified of all the lanthanides, otherwise a notoriously difficult group of elements to separate. A wide range of procedures have been devised over the years to exploit the difference. Among the better ones: # Leaching the mixed hydroxides with dilute nitric acid: the trivalent lanthanides dissolve in cerium-free condition, and tetravalent cerium remains in the insoluble residue as a concentrate to be further purified by other means. A variation on this uses hydrochloric acid and the calcined oxides from bastnaesite, but the separation is less sharp. # Precipitating cerium from a nitrate or chloride solution using potassium permanganate and sodium carbonate in a 1:4 molar ratio. # Boiling rare-earth nitrate solutions with potassium bromate and marble chips. Using the classical methods of rare-earth separation, there was a considerable advantage to a strategy of removing cerium from the mixture at the beginning. Cerium typically comprised 45% of the cerite or monazite rare earths, and removing it early greatly reduced the bulk of what needed to be further processed (or the cost of reagents to be associated with such processing). However, not all cerium purification methods relied on basicity. Ceric ammonium nitrate [ammonium hexanitratocerate(IV)] crystallization from nitric acid was one purification method. Cerium(IV) nitrate (hexanitratoceric acid) was more readily extractable into certain solvents (e.g. tri-n-butyl phosphate) than the trivalent lanthanides. However, modern practice in China seems to be to do purification of cerium by counter-current solvent extraction, in its trivalent form, just like the other lanthanides. Cerium(IV) is a strong oxidant under acidic conditions, but stable under alkaline conditions, when it is cerium(III) that becomes a strong reductant, easily oxidized by molecular dioxygen (or air). This ease of oxidation under alkaline conditions leads to the occasional geochemical parting of the ways between cerium and the trivalent light lanthanides under supergene weathering conditions, leading variously to the "negative cerium anomaly" or to the formation of the mineral cerianite. Air-oxidation of alkaline cerium(III) is the most economical way to get to cerium(IV), which can then be handled in acid solution. See also ''[[:Category:Cerium compounds]]'' == Isotopes == {{main|isotopes of cerium}} Naturally-occurring cerium is composed of 4 stable [[isotope]]s; <sup>136</sup>Ce, <sup>138</sup>Ce, <sup>140</sup>Ce, and <sup>142</sup>Ce with <sup>140</sup>Ce being the most abundant (88.48% [[natural abundance]]). <sup>136</sup>Ce and <sup>142</sup>Ce are predicted to be [[double beta decay|double beta]] active but no signs of activity were ever observed (for <sup>142</sup>Ce, the lower limit on [[half-life]] is 5×10<sup>16</sup> years). 26 [[radioisotope]]s have been characterized with the most long-lived being <sup>144</sup>Ce with a half-life of 284.893 days, <sup>139</sup>Ce with a half-life of 137.640 days, and <sup>141</sup>Ce with a half-life of 32.501 days. All of the remaining [[radioactive]] isotopes have half-lives that are less than 4 days and the majority of these have half-lives that are less than 10 minutes. This element also has 2 [[meta state]]s. The known isotopes of cerium range in [[atomic weight]] from 123 [[atomic mass unit|u]] (<sup>123</sup>Ce) to 152 u (<sup>152</sup>Ce). Cerium 144 is a high-yield product of [[nuclear fission]]; the [[Oak Ridge National Laboratory|ORNL]] [[Fission Product Pilot Plant]] separated substantial quantities of cerium-144 from reactor waste, and it was used in the [[Aircraft Nuclear Propulsion]] and [[Systems Nuclear Auxiliary Power Program|SNAP]] programs. == Precautions == Cerium, like all rare-earth metals, is of low to moderate toxicity. Cerium is a strong reducing agent and ignites spontaneously in air at 65 to 80 °C (150 to 175 °F). Fumes from cerium fires are toxic. Water should not be used to stop cerium fires, as cerium reacts with water to produce hydrogen gas. Workers exposed to cerium have experienced itching, sensitivity to heat, and skin lesions. Animals injected with large doses of cerium have died due to cardiovascular collapse. Cerium(IV) oxide is a powerful oxidizing agent at high temperatures and will react with combustible organic materials. While cerium is not radioactive, the impure commercial grade may contain traces of thorium, which is radioactive. Cerium serves no known biological function. ==Popular culture references== One chapter in [[Primo Levi]]'s book ''The Periodic Table'' called Cerium, the element saves the hero from starvation. ==References== *[http://periodic.lanl.gov/elements/58.html Los Alamos National Laboratory &ndash; Cerium] *[http://prola.aps.org/abstract/PRB/v19/i11/p5746_1 Lattice and spin dynamics of gamma-Ce] == External links == {{Commons|Cerium}} {{wiktionary|cerium}} *[http://www.webelements.com/webelements/elements/text/Ce/index.html WebElements.com &ndash; Cerium] *[http://education.jlab.org/itselemental/ele058.html It's Elemental &ndash; The Element Cerium] *[http://www.azom.com/details.asp?ArticleID=592 Cerium Properties and Applications] {{clear}} {{Compact periodic table}} [[Category:Chemical elements]] [[Category:Lanthanides]] [[Category:cerium compounds]] <!-- interwiki --> [[ar:سيريوم]] [[bn:সিরিয়াম]] [[be:Цэрый]] [[bs:Cerijum]] [[ca:Ceri]] [[cs:Cer]] [[co:Ceriu]] [[da:Cerium]] [[de:Cer]] [[et:Tseerium]] [[el:Δημήτριο]] [[es:Cerio]] [[eo:Cerio]] [[eu:Zerio (elementua)]] [[fr:Cérium]] [[fur:Ceri]] [[gv:Kerrium]] [[gl:Cerio]] [[ko:세륨]] [[hy:Ցերիում]] [[hr:Cerij]] [[io:Cerio]] [[id:Serium]] [[it:Cerio]] [[he:צריום]] [[ht:Seryòm]] [[la:Cerium]] [[lv:Cērijs]] [[lb:Cer]] [[lt:Ceris]] [[jbo:jinmrseri]] [[hu:Cérium]] [[ml:സെറിയം]] [[nl:Cerium]] [[ja:セリウム]] [[no:Cerium]] [[nn:Cerium]] [[oc:Cèri]] [[pl:Cer]] [[pt:Cério]] [[ro:Ceriu]] [[qu:Seryu]] [[ru:Церий]] [[scn:Ceriu]] [[sk:Cér]] [[sl:Cerij]] [[sr:Церијум]] [[sh:Cerijum]] [[stq:Cerium]] [[fi:Cerium]] [[sv:Cerium]] [[ta:சீரியம்]] [[th:ซีเรียม]] [[vi:Xeri]] [[tr:Seryum]] [[uk:Церій]] [[ur:Cerium]] [[zh-yue:鈰]] [[zh:铈]]