Rhodium 25601 226174209 2008-07-17T04:14:07Z Arkuat 29003 /* Characteristics */ section title per discussion at [[WP:WikiProject Elements]] :''[[Rh]] redirects here. For other uses, see [[rh (disambiguation)]]'' {{Elementbox_header | number=45 | symbol=Rh | name=rhodium | left=[[ruthenium]] | right=[[palladium]] | above=[[cobalt|Co]] | below=[[iridium|Ir]] | color1=#ffc0c0 | color2=black }} {{Elementbox_series | [[transition metal]]s }} {{Elementbox_groupperiodblock | group=9 | period=5 | block=d }} {{Elementbox_appearance_img | Rh,45| silvery white metallic }} {{Elementbox_atomicmass_gpm | [[1 E-25 kg|102.90550]][[List of elements by atomic mass|(2)]] }} {{Elementbox_econfig | &#91;[[krypton|Kr]]&#93; 4d<sup>8</sup> 5s<sup>1</sup> }} {{Elementbox_epershell | 2, 8, 18, 16, 1 }} {{Elementbox_section_physicalprop | color1=#ffc0c0 | color2=black }} {{Elementbox_phase | [[solid]] }} {{Elementbox_density_gpcm3nrt | 12.41 }} {{Elementbox_densityliq_gpcm3mp | 10.7 }} {{Elementbox_meltingpoint | k=2237 | c=1964 | f=3567 }} {{Elementbox_boilingpoint | k=3968 | c=3695 | f=6683 }} {{Elementbox_heatfusion_kjpmol | 26.59 }} {{Elementbox_heatvaporiz_kjpmol | 494 }} {{Elementbox_heatcapacity_jpmolkat25 | 24.98 }} {{Elementbox_vaporpressure_katpa | 2288 | 2496 | 2749 | 3063 | 3405 | 3997 | comment= }} {{Elementbox_section_atomicprop | color1=#ffc0c0 | color2=black }} {{Elementbox_crystalstruct | cubic face centered }} {{Elementbox_oxistates | 4, 3, 2, 1<ref>{{cite web|url=http://openmopac.net/data_normal/rhfr_jmol.html|title=Rhodium: rhodium(I) fluoride compound data|accessdate=2007-12-10|publisher=OpenMOPAC.net}}</ref><br />([[amphoteric]] oxide) }} {{Elementbox_electroneg_pauling | 2.28 }} {{Elementbox_ionizationenergies3 | 719.7 | 1740 | 2997 }} {{Elementbox_atomicradius_pm | [[1 E-10 m|135]] }} {{Elementbox_atomicradiuscalc_pm | [[1 E-10 m|173]] }} {{Elementbox_covalentradius_pm | [[1 E-10 m|135]] }} {{Elementbox_section_miscellaneous | color1=#ffc0c0 | color2=black }} {{Elementbox_magnetic | no data }} {{Elementbox_eresist_ohmmat0 | 43.3 n}} {{Elementbox_thermalcond_wpmkat300k | 150 }} {{Elementbox_thermalexpansion_umpmkat25 | 8.2 }} {{Elementbox_speedofsound_rodmpsat20 | 4700 }} {{Elementbox_youngsmodulus_gpa | 380 }} {{Elementbox_shearmodulus_gpa | 150 }} {{Elementbox_bulkmodulus_gpa | 275 }} {{Elementbox_poissonratio | 0.26 }} {{Elementbox_mohshardness | 6.0 }} {{Elementbox_vickershardness_mpa | 1246 }} {{Elementbox_brinellhardness_mpa | 1100 }} {{Elementbox_cas_number | 7440-16-6 }} {{Elementbox_isotopes_begin | color1=#ffc0c0 | color2=black }} {{Elementbox_isotopes_decay2 | mn=99 | sym=Rh | na=[[synthetic radioisotope|syn]] | hl=16.1 [[day|d]] | dm1=[[electron capture|ε]] | de1=- | pn1=99 | ps1=[[ruthenium|Ru]] | dm2=[[gamma ray|γ]] | de2=0.089, 0.353,<br />0.528 | pn2= | ps2=- }} {{Elementbox_isotopes_decay3 | mn=101[[nuclear isomer|m]] | sym=Rh | na=[[synthetic radioisotope|syn]] | hl=[[1 E5 s|4.34 d]] | dm1=[[electron capture|ε]] | de1=- | pn1=101 | ps1=[[ruthenium|Ru]] | dm2=[[Internal conversion|IT]] | de2=0.157 | pn2=101 | ps2=Rh | dm3=[[gamma ray|γ]] | de3=0.306, 0.545 | pn3= | ps3=- }} {{Elementbox_isotopes_decay2 | mn=101 | sym=Rh | na=[[synthetic radioisotope|syn]] | hl=[[1 E8 s|3.3 y]] | dm1=[[electron capture|ε]] | de1=- | pn1=101 | ps1=[[ruthenium|Ru]] | dm2=[[gamma ray|γ]] | de2=0.127, 0.198,<br />0.325 | pn2= | ps2=- }} {{Elementbox_isotopes_decay2 | mn=102[[nuclear isomer|m]] | sym=Rh | na=[[synthetic radioisotope|syn]] | hl=2.9 [[year|y]] | dm1=ε | de1=- | pn1=102 | ps1=[[ruthenium|Ru]] | dm2=[[gamma ray|γ]] | de2=0.475, 0.631,<br />0.697, 1.046 | pn2= | ps2=- }} {{Elementbox_isotopes_decay4 | mn=102 | sym=Rh | na=[[synthetic radioisotope|syn]] | hl=[[1 E7 s|207 d]] | dm1=[[electron capture|ε]] | de1=- | pn1=102 | ps1=[[ruthenium|Ru]] | dm2=[[Positron emission|β<sup>+</sup>]] | de2=0.826, 1.301 | pn2=102 | ps2=[[ruthenium|Ru]] | dm3=[[Beta decay|β<sup>-</sup>]] | de3=1.151 | pn3=102 | ps3=[[Palladium|Pd]] | dm4=[[gamma ray|γ]] | de4=0.475, 0.628 | pn4= | ps4=- }} {{Elementbox_isotopes_stable | mn=103 | sym=Rh | na=100% | n=58 }} {{Elementbox_isotopes_decay2 | mn=105 | sym=Rh | na=[[synthetic radioisotope|syn]] | hl=35.36 [[hour|h]] | dm1=[[Beta decay|β<sup>-</sup>]] | de1=0.247, 0.260,<br />0.566 | pn1=105 | ps1=[[Palladium|Pd]] | dm2=[[gamma ray|γ]] | de2=0.306, 0.318 | pn2= | ps2=- }} {{Elementbox_isotopes_end}} {{Elementbox_footer | color1=#ffc0c0 | color2=black }} '''Rhodium''' ({{pronEng|ˈroʊdiəm}}) is a [[chemical element]] with the symbol '''Rh''' and [[atomic number]] 45. A rare, silvery-white hard [[transition metal]] and a member of the [[platinum group]], rhodium is found in platinum ores and is used in [[alloy]]s with platinum and as a [[catalyst]]. It is usually the most expensive [[precious metal]]<ref>[http://www.taxfreegold.co.uk/preciousmetalpricesindx.html Precious Metal Prices Index<!-- Bot generated title -->]</ref>, though it is sometimes surpassed by [[rhenium]], depending on the market{{Fact|date=May 2008}}. == Characteristics == Rhodium is a hard silvery white and durable metal that has a high [[reflectance]]. Rhodium metal does not normally form an [[oxide]], even when heated. [[Oxygen]] is absorbed from the [[atmosphere]] at the [[melting point]] of rhodium, but on solidification the oxygen is released.<ref> {{cite book | last = Emsley | first = John | title = Nature's Building Blocks | edition = (Hardcover, First Edition) | publisher = [[Oxford University Press]] | date = 2001 | pages = page 363 | id = ISBN 0198503407 }}</ref> Rhodium has both a higher melting point and lower [[density]] than [[platinum]]. It is not attacked by [[acid]]s: it is completely insoluble in [[nitric acid]] and dissolves slightly in [[aqua regia]]. A complete dissolution of rhodium in powder form is only obtained in [[sulfuric acid]]. == Applications == The primary use of this element is as an alloying agent for hardening and improving the corrosion resistance<ref>{{Cite book | author=Cramer, Stephen; S., Jr Covino, Bernard | authorlink= | coauthors= | title=ASM handbook | date=1990 | publisher=ASM International | location=Materials Park, OH | isbn=0-87170-707-1 | pages=393 | url=http://books.google.com/books?id=QV0sWU2qF5oC&printsec=frontcover&source=gbs_summary_r&cad=0}}</ref> of [[platinum]] and [[palladium]]. These alloys are used in furnace windings, bushings for glass fiber production, [[thermocouple]] elements, [[electrode]]s for aircraft [[spark plug]]s, and laboratory crucibles.<ref>{{Cite book | author= Lide, David R | coauthors= | title= CRC handbook of chemistry and physics : a ready-reference book of chemical and physical data | date=2004 | publisher=CRC Press | location=Boca Raton | isbn=0-8493-0485-7 | pages=4-26 | url=http://books.google.com/books?id=WDll8hA006AC}}</ref> Other uses include: *It is used as an [[Switch#Contacts|electrical contact]] material due to its low [[electrical resistance]], low and stable [[contact resistance]], and its high [[corrosion]] resistance. *Plated rhodium, made by [[electroplating]] or evaporation, is extremely hard and is used for optical instruments. *This metal finds use in [[jewelry]] and for decorations. It is electroplated on [[white gold]] and platinum to give it a reflective white surface. This is known as rhodium flashing in the jewelry business. It also may be used in coating [[sterling silver]] in order to strengthen the metal from tarnish, as a result from the copper compound found in [[sterling silver]]. *It is also a highly useful [[catalyst]] in a number of industrial processes (notably it is used in the catalytic system of automobile [[catalytic converter]]s and for catalytic carbonylation of methanol to produce [[acetic acid]] by the [[Monsanto process]]). It is used to catalyse addition of hydrosilanes to a double bond, a process important in manufacture of certain silicone rubbers. *The complex of a rhodium ion with [[BINAP]] gives a widely used chiral catalyst for [[chiral synthesis]], as in the synthesis of [[menthol]]. *It is also used as a filter in [[mammography]] systems because of the characteristic x-rays it produces. *It is also used in high quality pen surfaces due to its high-resistance characteristics. These pens include Graf von Faber-Castell, Caran D'ache which are rather less famous than Montblanc, but produces very limited pens. == History == Rhodium ([[Greek language|Greek]] ''rhodon'' meaning "rose") was [[discovery of the chemical elements|discovered]] in [[1803]] by [[William Hyde Wollaston]],<ref>[http://www.webelements.com/webelements/elements/text/Rh/hist.html WebElements - The History of Rhodium]</ref> soon after his discovery of [[palladium]]. He made this discovery in [[England]] using crude [[platinum]] ore that he presumably obtained from [[South America]].<ref>{{Cite book | author= Lide, David R | coauthors= | title= CRC handbook of chemistry and physics : a ready-reference book of chemical and physical data | date=2004 | publisher=CRC Press | location=Boca Raton | isbn=0-8493-0485-7 | pages=4-26}}</ref> His procedure involved dissolving the ore in [[aqua regia]], neutralizing the acid with [[sodium hydroxide]] ([[sodium|Na]][[oxygen|O]][[hydrogen|H]]). He then precipitated the platinum by adding [[ammonium chloride]], [[nitrogen|N]]H<sub>4</sub>[[chlorine|Cl]], as [[ammonium chloroplatinate]]. The element palladium was removed as [[palladium cyanide]] after treating the solution with [[mercuric cyanide]]. The material that remained was a red [[rhodium(III) chloride]] (hence the name): rhodium metal was isolated via reduction with [[hydrogen]] gas. == Occurrence == ===Normal mining=== The industrial extraction of rhodium is complex as the metal occurs in ores mixed with other metals such as [[palladium]], [[silver]], [[platinum]], and [[gold]]. It is found in platinum ores and obtained free as a white inert metal which is very difficult to fuse. Principal sources of this element are located in South Africa, in river sands of the [[Ural Mountains]], in North and South America and also in the [[copper]]-[[nickel sulfide]] mining area of the [[Sudbury, Ontario]] region. Although the quantity at Sudbury is very small, the large amount of nickel ore processed makes rhodium recovery cost effective. The main exporter of rhodium is South Africa (>80%) followed by Russia. The annual world production of this element is only about 25 [[ton]]s and there are very few rhodium [[mineral]]s. As of October 2007, rhodium cost approximately eight times more than gold, 450 times more than silver, and 27,250 times more than copper by weight. Rhodium's typical historical price is about $1,000/troy oz,<ref>[http://periodic.lanl.gov/elements/45.html http://periodic.lanl.gov/elements/45.html]</ref> but in recent years it has increased to about $9500/troy oz.<ref>[http://www.kitco.com/charts/rhodium.html KITCO Rhodium Price Charts]</ref> ===As a fission product=== It is also possible to extract rhodium from [[used nuclear fuel]], which contains rhodium (1 kg of the [[fission products]] of <sup>235</sup>U contain 13.3 grams of <sup>103</sup>Rh). So as a typical used fuel is 3% fission products by weight it will contain about 400 grams of rhodium per ton of used fuel. The longest lived radioisotope of rhodium is <sup>102m</sup>Rh which has a half life of 2.9 years, while the ground state (<sup>102</sup>Rh)has a half life of 207 days. Each kilo of fission rhodium will contain 6.62 ng of <sup>102</sup>Rh and 3.68 ng of <sup>102m</sup>Rh. As <sup>102</sup>Rh decays by [[beta decay]] to either <sup>102</sup>Ru (80%) (some [[positron emission]] will occur) or <sup>102</sup>Pd (20%) (some [[gamma ray]] photons with about 500 keV are generated) and the excited state decays by beta decay (electron capture) to <sup>102</sup>Ru (some [[gamma ray]] photons with about 1 MeV are generated). If the fission occurs in an instant then 13.3 grams of rhodium will contain 67.1 MBq (1.81 mCi) of <sup>102</sup>Rh and 10.8 MBq (291 μCi) of <sup>102m</sup>Rh. As it is normal to allow used nuclear fuel to stand for about five years before reprocessing, much of this activity will decay away leaving 4.7 MBq of <sup>102</sup>Rh and 5.0 MBq of <sup>102m</sup>Rh. If the rhodium metal was then left for 20 years after fission, then the 13.3 grams of rhodium metal would contain 1.3 kBq of <sup>102</sup>Rh and 500 kBq of <sup>102m</sup>Rh. At first glance the rhodium might be adding to the resource value of reprocessed fission waste, but the cost of the separation of the rhodium from the other metals needs to be considered. == Isotopes == [[Image:Activity of pt group metals from uranium fission.png|thumb|450px|right|The radioactivity in MBq per gram of each of the platinum group metals which are formed by the fission of uranium, ruthenium is the most radioactive. Palladium has an almost constant activity due to the very long lived [[Pd-107|<sup>107</sup>Pd]], while rhodium is the least radioactive]] {{main|isotopes of rhodium}} Naturally occurring rhodium is composed of only one [[isotope]], <sup>103</sup>Rh. The most stable [[radioisotope]]s are <sup>101</sup>Rh with a [[half-life]] of 3.3 years, <sup>102</sup>Rh with a [[half-life]] of 207 days, <sup>102m</sup>Rh with a [[half-life]] of 2.9 years, and <sup>99</sup>Rh with a half-life of 16.1 days. Twenty other radioisotopes have been characterized with [[atomic weight]]s ranging from 92.926 [[atomic mass unit|u]] (<sup>93</sup>Rh) to 116.925 u (<sup>117</sup>Rh). Most of these have half-lifes that are less than an hour except <sup>100</sup>Rh (half-life: 20.8 hours) and <sup>105</sup>Rh (half-life: 35.36 hours). There are also numerous [[meta state]]s with the most stable being <sup>102m</sup>Rh (0.141 MeV) with a half-life of about 207 days and <sup>101m</sup>Rh (0.157 MeV) with a half-life of 4.34 days. See [[isotopes of rhodium]]. The primary [[decay mode]] before the only stable isotope, <sup>103</sup>Rh, is [[electron capture]] and the primary mode after is [[beta emission]]. The primary [[decay product]] before <sup>103</sup>Rh is [[ruthenium]] and the primary product after is [[palladium]]. == Precautions == Rhodium metal is, as a noble metal, inert. However, when rhodium is chemically bound, it is reactive. Rhodium compounds are not often encountered by most people and should be considered to be [[toxic]] and possibly [[carcinogen]]ic{{Fact|date=September 2007}}. Lethal intake (LD50) for rats is 12.6 mg/kg of rhodium chloride (RhCl<sub>3</sub>){{Fact|date=September 2007}}. Rhodium compounds can strongly stain human skin. The element plays no biological role in humans. If used in elemental form rather than as compounds, the metal is harmless. == Symbolic uses == Rhodium has been used for honours, or to symbolize wealth, when more commonly used metals such as silver, gold, or platinum are deemed insufficient. In 1979 the ''[[Guinness Book of World Records]]'' gave [[Paul McCartney]] a rhodium-plated disc for being history's all-time best-selling songwriter and recording artist. Guinness has also noted items such as the world's "Most Expensive Pen" or "Most Expensive Board Game" as containing rhodium. ==See also== *[[:category:Rhodium compounds|Rhodium compounds]] ==References== <references /> ==External links== *[http://www.webelements.com/webelements/elements/text/Rh/index.html WebElements.com &ndash; Rhodium] *[http://www.kitco.com/market/ Current Rhodium price] *[http://www.americanelements.com/rh.html Rhodium Technical and Safety Data] *[http://periodic.lanl.gov/elements/45.html Los Alamos National Laboratory &ndash; Rhodium] *[http://www.searchmining.net/ASPM/EUISearch.do?qgeneral=rhodium&searchType=defLink&q=&tabid= Search Rhodium on the search engine dedicated to the mining industry] [[Image:Rhodium foil and wire.jpg|left|thumb|Rhodium foil and wire]] {{Commons|Rhodium}} {{wiktionary|rhodium}} {{clear}} {{compact periodic table}} {{Jewellery Materials}} [[Category:Rhodium| ]] [[Category:Chemical elements]] [[Category:Transition metals]] [[af:Rodium]] [[ar:روديوم]] [[bn:রোহডিয়াম]] [[be:Родый]] [[bs:Rodijum]] [[ca:Rodi]] [[cs:Rhodium]] [[co:Rodiu]] [[da:Rhodium]] [[de:Rhodium]] [[et:Roodium]] [[el:Ρόδιο]] [[es:Rodio]] [[eo:Rodio]] [[eu:Rodio]] [[fa:رادیوم]] [[fr:Rhodium]] [[fur:Rodi]] [[gv:Roydjum]] [[gl:Rodio]] [[ko:로듐]] [[hy:Ռոդիում]] [[hr:Rodij]] [[io:Rodio]] [[id:Rodium]] [[is:Ródín]] [[it:Rodio]] [[he:רודיום]] [[jv:Rodium]] [[sw:Rodi]] [[ht:Rodyòm]] [[ku:Rodyûm]] [[la:Rhodium]] [[lv:Rodijs]] [[lb:Rhodium]] [[lt:Rodis]] [[jbo:zgujinme]] [[hu:Ródium]] [[ml:റോഡിയം]] [[mr:र्‍होडियम]] [[nl:Rhodium]] [[ja:ロジウム]] [[no:Rhodium]] [[nn:Rhodium]] [[oc:Ròdi]] [[uz:Rodiy]] [[pl:Rod (pierwiastek)]] [[pt:Ródio]] [[ro:Rodiu]] [[ru:Родий]] [[scn:Rodiu]] [[simple:Rhodium]] [[sk:Ródium]] [[sl:Rodij]] [[sr:Родијум]] [[sh:Rodijum]] [[fi:Rodium]] [[sv:Rodium]] [[ta:ரோடியம்]] [[th:โรเดียม]] [[vi:Rhodi]] [[tr:Rodyum]] [[uk:Родій]] [[zh:铑]]