関: Rh

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a white hard metallic element that is one of the platinum group and is found in platinum ores; used in alloys with platinum (同)Rh, atomic number 45

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ロジウム(金属元素;化学記号は『RH』)
rhodiumの化学記号

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/07/23 06:37:57」(JST)

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Rhodium is a chemical element with symbol Rh and atomic number 45. It is a rare, silvery-white, hard, and chemically inert transition metal. It is a member of the platinum group. It has only one naturally occurring isotope, ¹⁰³Rh. Naturally occurring rhodium is usually found as the free metal, alloyed with similar metals, and rarely as a chemical compound in minerals such as bowieite and rhodplumsite. It is one of the rarest and most valuable precious metals.

Rhodium is a noble metal, resistant to corrosion, found in platinum- or nickel ores together with the other members of the platinum group metals. It was discovered in 1803 by William Hyde Wollaston in one such ore, and named for the rose color of one of its chlorine compounds, produced after it reacted with the powerful acid mixture aqua regia.

The element's major use (approximately 80% of world rhodium production) is as one of the catalysts in the three-way catalytic converters in automobiles. Because rhodium metal is inert against corrosion and most aggressive chemicals, and because of its rarity, rhodium is usually alloyed with platinum or palladium and applied in high-temperature and corrosion-resistive coatings. White gold is often plated with a thin rhodium layer to improve its appearance while sterling silver is often rhodium-plated for tarnish resistance.

Rhodium detectors are used in nuclear reactors to measure the neutron flux level.

History

William Hyde Wollaston

Rhodium (Greek rhodon (ῥόδον) meaning "rose") was discovered in 1803 by William Hyde Wollaston,^[4] soon after his discovery of palladium.^[5]^[6]^[7] He used crude platinum ore presumably obtained from South America.^[8] His procedure involved dissolving the ore in aqua regia and neutralizing the acid with sodium hydroxide (NaOH). He then precipitated the platinum as ammonium chloroplatinate by adding ammonium chloride (NH
4Cl). Most other metals like copper, lead, palladium and rhodium were precipitated with zinc. Diluted nitric acid dissolved all but palladium and rhodium, which were dissolved in aqua regia, and the rhodium was precipitated by the addition of sodium chloride as Na
3[RhCl
6]·nH
2O. After being washed with ethanol, the rose-red precipitate was reacted with zinc, which displaced the rhodium in the ionic compound and thereby released the rhodium as free metal.^[9]

After the discovery, the rare element had only minor applications; for example, by the turn of the century, rhodium-containing thermocouples were used to measure temperatures up to 1800 °C.^[10]^[11] The first major application was electroplating for decorative uses and as corrosion-resistant coating.^[12] The introduction of the three-way catalytic converter by Volvo in 1976 increased the demand for rhodium. The previous catalytic converters used platinum or palladium, while the three-way catalytic converter used rhodium to reduce the amount of NO_x in the exhaust.^[13]^[14]^[15]

Characteristics

Z	Element	No. of electrons/shell
27	cobalt	2, 8, 15, 2
45	rhodium	2, 8, 18, 16, 1
77	iridium	2, 8, 18, 32, 15, 2
109	meitnerium	2, 8, 18, 32, 32, 15, 2 (predicted)

Rhodium is a hard, silvery, durable metal that has a high reflectance. Rhodium metal does not normally form an oxide, even when heated.^[16] Oxygen is absorbed from the atmosphere only at the melting point of rhodium, but is released on solidification.^[17] Rhodium has both a higher melting point and lower density than platinum. It is not attacked by most acids: it is completely insoluble in nitric acid and dissolves slightly in aqua regia.

Chemical properties

Wilkinson's catalyst

Rhodium belongs to group 9 of the periodic table but has an atypical configuration in its outermost electron shells compared to the rest of the members. This can also be observed in the neighborhood of niobium (41), ruthenium (44), and palladium (46).

Oxidation states of rhodium
+0	Rh 4(CO) 12
+1	RhCl(PH 3) 2
+2	Rh 2(O 2CCH 3) 4
+3	RhCl 3, Rh 2O 3
+4	RhF 4, RhO 2
+5	RhF 5, Sr 3LiRhO 6
+6	RhF 6

The common oxidation state of rhodium is +3, but oxidation states from +0 to +6 are also observed.^[18]

Unlike ruthenium and osmium, rhodium forms no volatile oxygen compounds. The known stable oxides include Rh
2O
3, RhO
2, RhO
2·xH
2O, Na
2RhO
3, Sr
3LiRhO
6 and Sr
3NaRhO
6.^[19] Halogen compounds are known in nearly the full range of possible oxidation states. Rhodium(III) chloride, rhodium(IV) fluoride, rhodium(V) fluoride and rhodium(VI) fluoride are some examples. The lower oxidation states are only stable if ligands are present.^[20]

The best-known rhodium-halogen compound is the Wilkinson's catalyst chlorotris(triphenylphosphine)rhodium(I). This catalyst is used, for example, in the hydroformylation or hydrogenation of alkenes.^[21]

Isotopes

Naturally occurring rhodium is composed of only one isotope, ¹⁰³Rh. The most stable radioisotopes are ¹⁰¹Rh with a half-life of 3.3 years, ¹⁰²Rh with a half-life of 207 days, ^102mRh with a half-life of 2.9 years, and ⁹⁹Rh with a half-life of 16.1 days. Twenty other radioisotopes have been characterized with atomic weights ranging from 92.926 u (⁹³Rh) to 116.925 u (¹¹⁷Rh). Most of these have half-lives shorter than an hour, except ¹⁰⁰Rh (half-life: 20.8 hours) and ¹⁰⁵Rh (half-life: 35.36 hours). There are also numerous meta states, the most stable being ^102mRh (0.141 MeV) with a half-life of about 2.9 years and ^101mRh (0.157 MeV) with a half-life of 4.34 days (see isotopes of rhodium).^[22]

The primary decay mode before the only stable isotope, ¹⁰³Rh, is electron capture and the primary mode after is beta emission. The primary decay product before ¹⁰³Rh is ruthenium and the primary product after is palladium.^[23]

Occurrence

Rhodium is one of the rarest elements in the Earth's crust, of which it comprises an estimated 0.0002 parts per million (2 × 10⁻¹⁰).^[24] Its rarity affects its price, and thus its usage in commercial applications.

Mining and price

Rh price evolution.

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 extracted as a white inert metal which is very difficult to fuse. Principal sources are located in South Africa; in river sands of the Ural Mountains; and in North America, including the copper-nickel sulfide mining area of the Sudbury, Ontario, region. Although the quantity at Sudbury is very small, the large amount of processed nickel ore makes rhodium recovery cost-effective.

The main exporter of rhodium is South Africa (approximately 80% in 2010) followed by Russia.^[25] The annual world production of this element is 30 tonnes and there are very few rhodium-bearing minerals. The price of rhodium is historically highly variable. In 2007, rhodium cost approximately eight times more than gold, 450 times more than silver, and 27,250 times more than copper by weight. In 2008, the price briefly rose above $10,000 per ounce ($350,000 per kilogram). The economic slowdown of the 3rd quarter of 2008 pushed rhodium prices sharply back below $1,000 per ounce ($35,000 per kilogram); they rebounded to $2,750 by early 2010 ($97,000 per kilogram) (over twice the gold price), but in late 2013, the prices were a bit lower than $1000.^[26]

Used nuclear fuels

Rhodium is a fission product of uranium-235; therefore, each kilogram of fission products contains significant amounts of the lighter platinum group metals including rhodium. Used nuclear fuel might be a possible source for rhodium. However, the extraction is complex and expensive, and the also present radioactive isotopes of rhodium would require a storage for several half-lives of the longest-lived decaying isotope (i.e. about 10 years) to reduce the radioactivity. This makes this source of rhodium unattractive and no large-scale extraction has been attempted.^[27]^[28]^[29]

Applications

The primary use of this element is in automobiles as a catalytic converter, which changes harmful unburned hydrocarbons, carbon monoxide, and nitrogen oxide emissions from the engine into less noxious gases. Of 30,000 kg of rhodium consumed worldwide in 2012, some 24,300 kg (81%) went into and 8,060 kg recovered from this application. About 964 kg of rhodium was used in the glass industry, mostly for production of fiberglass and flat-panel glass, and 2,520 kg in the chemical industry.^[25]

Catalyst

In 2012, 81% of the world production of rhodium was consumed to produce three-way catalytic converters.^[25] Rhodium shows some advantages over the other platinum metals in the reduction of nitrogen oxides to nitrogen and oxygen:^[30]

2 NO
x → x O
2 + N
2

Rhodium-based catalysts are used in a number of industrial processes; notably, in the automobile catalytic converters and for catalytic carbonylation of methanol to produce acetic acid by the Monsanto process.^[31] It is also used to catalyze addition of hydrosilanes to molecular double bonds, a process important in manufacture of certain silicone rubbers.^[32] Rhodium catalysts are also used to reduce benzene to cyclohexane.^[33]

The complex of a rhodium ion with BINAP gives a widely used chiral catalyst for chiral synthesis, as in the synthesis of menthol.^[34]

Ornamental uses

Rhodium finds use in jewelry and for decorations. It is electroplated on white gold and platinum to give it a reflective white surface at time of sale, after which the thin layer wears away with use. This is known as rhodium flashing in the jewelry business. It may also be used in coating sterling silver to protect against tarnish, which is silver sulfide (Ag₂S) produced from the atmospheric hydrogen sulfide (H₂S). Solid (pure) rhodium jewelry is very rare because the metal has both a high melting point and poor malleability, making such jewelry very hard to fabricate — rather than due to its high price.^[35] Additionally, its typically higher cost assures that most of its jewelry usage is in the form of tiny amounts of powder, commonly called rhodium sponge, dissolved into electroplating solutions.

Rhodium has also been used for honors or to signify elite status, when more commonly used metals such as silver, gold or platinum were 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.^[36]

Other uses

Rhodium is used as an alloying agent for hardening and improving the corrosion resistance^[16] of platinum and palladium. These alloys are used in furnace windings, bushings for glass fiber production, thermocouple elements, electrodes for aircraft spark plugs, and laboratory crucibles.^[37] Other uses include:

An electrical contact material due to its low electrical resistance, low and stable contact resistance, and high corrosion resistance.^[38]
Plated rhodium, made by electroplating or evaporation, is extremely hard and is used for optical instruments.^[39]
It is also used as a filter in mammography systems because of the characteristic X-rays it produces.^[40]
Rhodium neutron detectors are used in combustion engineering nuclear reactors to measure neutron flux levels – a method that requires a digital filter to determine the current neutron flux level, as there are three signals generated: immediate, a few seconds later, and a minute later, each with its own signal level, and all three are combined in the rhodium detector signals. The three Palo Verde nuclear reactors each have 305 rhodium neutron detectors, 61 detectors on each of five vertical levels, providing an accurate 3D "picture" of reactivity and allowing fine tuning to most economically burn the nuclear fuel.^[41]

A 78 g sample of rhodium
Cross section of a metal-core catalytic converter
Rhodium-plated white gold wedding ring
Rhodium foil and wire

Precautions

Being a noble metal, pure rhodium is inert. However, chemical complexes of rhodium can be reactive. Median lethal dose (LD₅₀) for rats is 198 mg of rhodium chloride (RhCl
3) per kilogram of body weight.^[42] Like the other noble metals, all of which are too inert to occur as chemical compounds in nature, rhodium has not been found to play any biological role. If used in elemental form rather than as compounds, the metal is harmless.^[43]

References

^ Standard Atomic Weights 2013. Commission on Isotopic Abundances and Atomic Weights
^ "Rhodium: rhodium(I) fluoride compound data". OpenMOPAC.net. Retrieved 2007-12-10.
^ Lide, D. R., ed. (2005). "Magnetic susceptibility of the elements and inorganic compounds". CRC Handbook of Chemistry and Physics (PDF) (86th ed.). Boca Raton (FL): CRC Press. ISBN 0-8493-0486-5.
^ Wollaston, W. H. (1804). "On a New Metal, Found in Crude Platina". Philosophical Transactions of the Royal Society of London 94: 419–430. doi:10.1098/rstl.1804.0019.
^ Griffith, W. P. (2003). "Rhodium and Palladium – Events Surrounding Its Discovery". Platinum Metals Review 47 (4): 175–183.
^ Wollaston, W. H. (1805). "On the Discovery of Palladium; With Observations on Other Substances Found with Platina". Philosophical Transactions of the Royal Society of London 95: 316–330. doi:10.1098/rstl.1805.0024.
^ Usselman, Melvyn (1978). "The Wollaston/Chenevix controversy over the elemental nature of palladium: A curious episode in the history of chemistry". Annals of Science 35 (6): 551–579. doi:10.1080/00033797800200431.
^ Lide, David R. (2004). CRC handbook of chemistry and physics: a ready-reference book of chemical and physical data. Boca Raton: CRC Press. pp. 4–26. ISBN 0-8493-0485-7.
^ Griffith, W. P. (2003). "Bicentenary of Four Platinum Group Metals: Osmium and iridium – events surrounding their discoveries". Platinum Metals Review 47 (4): 175–183.
^ Hulett, G. A.; Berger, H. W. (1904). "VOLATILIZATION OF PLATINUM doi = 10.1021/ja02001a012". Journal of the American Chemical Society 26 (11): 1512. doi:10.1021/ja02001a012.
^ Measurement, Astm Committee E.2.0. on Temperature (1993). "Platinum Type". Manual on the use of thermocouples in temperature measurement. ASTM International. ISBN 978-0-8031-1466-1.
^ Kushner, Joseph B. (1940). "Modern rhodium plating". Metals and Alloys 11: 137–140.
^ Amatayakul, W; Ramnäs, Olle (2001). "Life cycle assessment of a catalytic converter for passenger cars". Journal of Cleaner Production 9 (5): 395. doi:10.1016/S0959-6526(00)00082-2.
^ Heck, R; Farrauto, Robert J. (2001). "Automobile exhaust catalysts". Applied Catalysis A: General 221: 443. doi:10.1016/S0926-860X(01)00818-3.
^ Heck, R; Gulati, Suresh; Farrauto, Robert J. (2001). "The application of monoliths for gas phase catalytic reactions". Chemical Engineering Journal 82: 149. doi:10.1016/S1385-8947(00)00365-X.
^ ^a ^b Cramer, Stephen D.; Covino, Jr., Bernard S., eds. (1990). ASM handbook. Materials Park, OH: ASM International. pp. 393–396. ISBN 0-87170-707-1.
^ Emsley, John (2001). Nature's Building Blocks ((Hardcover, First Edition) ed.). Oxford University Press. p. 363. ISBN 0-19-850340-7.
^ Holleman, Arnold F.; Wiberg, Egon; Wiberg, Nils (1985). Lehrbuch der Anorganischen Chemie (91–100 ed.). Walter de Gruyter. pp. 1056–1057. ISBN 3-11-007511-3.
^ Reisner, B. A.; Stacy, A. M. (1998). "Sr
3ARhO
6 (A = Li, Na): Crystallization of a Rhodium(V) Oxide from Molten Hydroxide". Of the American Chemical Society 120 (37): 9682–9989. doi:10.1021/ja974231q.
^ Griffith, W. P. The Rarer Platinum Metals, John Wiley and Sons: New York, 1976, p. 313.
^ Osborn, J. A.; Jardine, F. H.; Young, J. F.; Wilkinson, G. (1966). "The Preparation and Properties of Tris(triphenylphosphine)halogenorhodium(I) and Some Reactions Thereof Including Catalytic Homogeneous Hydrogenation of Olefins and Acetylenes and Their Derivatives". Journal of the Chemical Society A: 1711–1732. doi:10.1039/J19660001711.
^ Audi, G.; Bersillon, O.; Blachot, J.; Wapstra, A.H. (2003). "The NUBASE Evaluation of Nuclear and Decay Properties". Nuclear Physics A (Atomic Mass Data Center) 729: 3–128. Bibcode:2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001.
^ David R. Lide (ed.), Norman E. Holden in CRC Handbook of Chemistry and Physics, 85th Edition CRC Press. Boca Raton, Florida (2005). Section 11, Table of the Isotopes.
^ Barbalace, Kenneth, "Table of Elements". Environmental Chemistry.com; retrieved 2007-04-14.
^ ^a ^b ^c Loferski, Patricia J. (2013). "Commodity Report: Platinum-Group Metals" (PDF). United States Geological Survey. Retrieved 2012-07-16.
^ "Rhodium". www.kitco.com. Retrieved 2010-06-09.
^ Kolarik, Zdenek; Renard, Edouard V. (2005). "Potential Applications of Fission Platinoids in Industry" (PDF). Platinum Metals Review 49 (2): 79. doi:10.1595/147106705X35263.
^ Kolarik, Zdenek; Renard, Edouard V. (2003). "Recovery of Value Fission Platinoids from Spent Nuclear Fuel. Part I PART I: General Considerations and Basic Chemistry" (PDF). Platinum Metals Review 47 (2): 74–87.
^ Kolarik, Zdenek; Renard, Edouard V. (2003). "Recovery of Value Fission Platinoids from Spent Nuclear Fuel. Part II: Separation Process" (PDF). Platinum Metals Review 47 (2): 123–131.
^ Shelef, M.; Graham, G. W. (1994). "Why Rhodium in Automotive Three-Way Catalysts?". Catalysis Reviews 36 (3): 433–457. doi:10.1080/01614949408009468.
^ Roth, James F. (1975). "Rhodium Catalysed Carbonylation of Methanol" (PDF). Platinum Metals Review 19 (1 January): 12–14.
^ Heidingsfeldova, M. & Capka, M. (2003). "Rhodium complexes as catalysts for hydrosilylation crosslinking of silicone rubber". Journal of Applied Polymer Science 30 (5): 1837. doi:10.1002/app.1985.070300505.
^ Halligudi, S. B. et al. (1992). "Hydrogenation of benzene to cyclohexane catalyzed by rhodium(I) complex supported on montmorillonite clay". Reaction Kinetics and Catalysis Letters 48 (2): 547. doi:10.1007/BF02162706.
^ Akutagawa, S. (1995). "Asymmetric synthesis by metal BINAP catalysts". Applied Catalysis A 128 (2): 171. doi:10.1016/0926-860X(95)00097-6.
^ Fischer, Torkel; Fregert, S; Gruvberger, B; Rystedt, I (1984). "Contact sensitivity to nickel in white gold". Contact Dermatitis 10 (1): 23–24. doi:10.1111/j.1600-0536.1984.tb00056.x. PMID 6705515.
^ "Hit & Run: Ring the changes". The Independent (London). 2008-12-02. Retrieved 2009-06-06.
^ Lide, David R (2004). CRC handbook of chemistry and physics 2004–2005: a ready-reference book of chemical and physical data (85th ed.). Boca Raton: CRC Press. pp. 4–26. ISBN 0-8493-0485-7.
^ Weisberg, Alfred M. (1999). "Rhodium plating". Metal Finishing 97 (1): 296–299. doi:10.1016/S0026-0576(00)83088-3.
^ Smith, Warren J. (2007). "Reflectors". Modern optical engineering: the design of optical systems. McGraw-Hill. pp. 247–248. ISBN 978-0-07-147687-4.
^ McDonagh, C P et al. (1984). "Optimum x-ray spectra for mammography: choice of K-edge filters for tungsten anode tubes". Phys. Med. Biol. 29 (3): 249. Bibcode:1984PMB....29..249M. doi:10.1088/0031-9155/29/3/004.
^ Sokolov, A. P.; Pochivalin, G. P.; Shipovskikh, Yu. M.; Garusov, Yu. V.; Chernikov, O. G.; Shevchenko, V. G. (1993). "Rhodium self-powered detector for monitoring neutron fluence, energy production, and isotopic composition of fuel". Atomic Energy 74 (5): 365–367. doi:10.1007/BF00844622.
^ Landolt, Robert R.; Berk Harold W.; Russell, Henry T. (1972). "Studies on the toxicity of rhodium trichloride in rats and rabbits". Toxicology and Applied Pharmacology 21 (4): 589–590. doi:10.1016/0041-008X(72)90016-6. PMID 5047055.
^ Leikin, Jerrold B.; Paloucek Frank P. (2008). Poisoning and Toxicology Handbook. Informa Health Care. p. 846. ISBN 978-1-4200-4479-9.

External links

Rhodium at The Periodic Table of Videos (University of Nottingham)
Current Rhodium price
Rhodium Technical and Safety Data
CDC - NIOSH Pocket Guide to Chemical Hazards

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1. ぶどう膜黒色腫および結膜悪性黒色腫の初期マネージメント initial management of uveal and conjunctival melanomas

English Journal

Decoration of reduced graphene oxide with rhodium nanoparticles for the design of a sensitive electrochemical enzyme biosensor for 17β-estradiol.

Povedano E1, Cincotto FH2, Parrado C1, Díez P1, Sánchez A3, Canevari TC4, Machado SA5, Pingarrón JM1, Villalonga R6.
Biosensors & bioelectronics.Biosens Bioelectron.2017 Mar 15;89(Pt 1):343-351. doi: 10.1016/j.bios.2016.07.018. Epub 2016 Jul 7.
A novel nanocomposite material consisting of reduced graphene oxide/Rh nanoparticles was prepared by a one-pot reaction process. The strategy involved the simultaneous reduction of RhCl3 and graphene oxide with NaBH4 and the in situ deposition of the metal nanoparticles on the 2D carbon nanomaterial
PMID 27450540

Rhodium catalyzed synthesis of difluoromethyl cyclopropanes.

Hock KJ1, Mertens L, Koenigs RM.
Chemical communications (Cambridge, England).Chem Commun (Camb).2016 Dec 11;52(95):13783-13786. Epub 2016 Nov 9.
Difluoromethyl-substituted cyclopropanes still remain one of the most challenging class of substrates. Despite significant progress in modern chemistry, an atom-economic and concise synthesis has not been described to date. Herein, we describe the first method for their catalytic, one-step synthesis
PMID 27826609

Polymer versus phosphine stabilized Rh nanoparticles as components of supported catalysts: implication in the hydrogenation of cyclohexene model molecule.

Ibrahim M1, Garcia MA, Vono LL, Guerrero M, Lecante P, Rossi LM, Philippot K.
Dalton transactions (Cambridge, England : 2003).Dalton Trans.2016 Nov 28;45(44):17782-17791. Epub 2016 Oct 21.
The solution synthesis of rhodium nanoparticles (Rh NPs) was achieved from the organometallic complex [Rh(η3-C3H5)3] under mild reaction conditions in the presence of a polymer (PVP), a monophosphine (PPh3) and a diphosphine (dppb) as a stabilizer, leading to very small Rh NPs of 2.2, 1.3 and 1.7 n
PMID 27767201

A DFT study of the role of water in the rhodium-catalyzed hydrogenation of acetone.

Polo V1, Schrock RR2, Oro LA3.
Chemical communications (Cambridge, England).Chem Commun (Camb).2016 Nov 24;52(96):13881-13884.
The positive effect of the addition of water to acetone hydrogenation by [RhH2(PR3)2S2]+ catalysts has been studied by DFT calculations. The studied energetic profiles reveal that the more favourable mechanistic path involves a hydride migration to the ketone followed by a reductive elimination that
PMID 27841377

Japanese Journal

ロジウム触媒を用いる有機硫黄・リン化合物の平衡制御合成

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Heterocycles 85(5), 1017-1043, 2012-05-01
NAID 40019238527

Related Pictures

★リンクテーブル★

リンク元	「Rh」「ロジウム」

「Rh」

Rhodium, ₄₅Rh
General properties
Name, symbol	rhodium, Rh
Pronunciation	/ˈroʊdiəm/; ROH-dee-əm
Appearance	silvery white metallic
Rhodium in the periodic table
	ruthenium ← rhodium → palladium
Atomic number	45
Standard atomic weight (±) (Ar)	102.90550(2)
Element category	transition metal
Group, block	group 9, d-block
Period	period 5
Electron configuration	[Kr] 4d8 5s1
per shell	2, 8, 18, 16, 1
Physical properties
Phase	solid
Melting point	2237 K (1964 °C, 3567 °F)
Boiling point	3968 K (3695 °C, 6683 °F)
Density near r.t.	12.41 g/cm3
when liquid, at m.p.	10.7 g/cm3
Heat of fusion	26.59 kJ/mol
Heat of vaporization	493 kJ/mol
Molar heat capacity	24.98 J/(mol·K)
Atomic properties
Oxidation states	6, 5, 4, 3, 2, 1, −1 (an amphoteric oxide)
Electronegativity	Pauling scale: 2.28
Ionization energies	1st: 719.7 kJ/mol; 2nd: 1740 kJ/mol; 3rd: 2997 kJ/mol
Atomic radius	empirical: 134 pm
Covalent radius	142±7 pm
Miscellanea
Crystal structure	face-centered cubic (fcc)
Speed of sound thin rod	4700 m/s (at 20 °C)
Thermal expansion	8.2 µm/(m·K) (at 25 °C)
Thermal conductivity	150 W/(m·K)
Electrical resistivity	43.3 nΩ·m (at 0 °C)
Magnetic ordering	paramagnetic
Young's modulus	380 GPa
Shear modulus	150 GPa
Bulk modulus	275 GPa
Poisson ratio	0.26
Mohs hardness	6.0
Vickers hardness	1100–8000 MPa
Brinell hardness	980–1350 MPa
CAS Registry Number	7440-16-6
History
Discovery and first isolation	William Hyde Wollaston (1804)
Most stable isotopes
	Main article: Isotopes of rhodium
	Decay modes in parentheses are predicted, but have not yet been observed
	view; talk; edit; · references

　　[★]

「ロジウム」

　　[★]

英: rhodium、Rh
関: Rh抗原

[IUPAC-1] Standard Atomic Weights 2013. Commission on Isotopic Abundances and Atomic Weights

[2] "Rhodium: rhodium(I) fluoride compound data". OpenMOPAC.net. Retrieved 2007-12-10.

[3] Lide, D. R., ed. (2005). "Magnetic susceptibility of the elements and inorganic compounds". CRC Handbook of Chemistry and Physics (PDF) (86th ed.). Boca Raton (FL): CRC Press. ISBN 0-8493-0486-5.

[4] Wollaston, W. H. (1804). "On a New Metal, Found in Crude Platina". Philosophical Transactions of the Royal Society of London 94: 419–430. doi:10.1098/rstl.1804.0019.

[5] Griffith, W. P. (2003). "Rhodium and Palladium – Events Surrounding Its Discovery". Platinum Metals Review 47 (4): 175–183.

[6] Wollaston, W. H. (1805). "On the Discovery of Palladium; With Observations on Other Substances Found with Platina". Philosophical Transactions of the Royal Society of London 95: 316–330. doi:10.1098/rstl.1805.0024.

[contr-7] Usselman, Melvyn (1978). "The Wollaston/Chenevix controversy over the elemental nature of palladium: A curious episode in the history of chemistry". Annals of Science 35 (6): 551–579. doi:10.1080/00033797800200431.

[8] Lide, David R. (2004). CRC handbook of chemistry and physics: a ready-reference book of chemical and physical data. Boca Raton: CRC Press. pp. 4–26. ISBN 0-8493-0485-7.

[griffith-9] Griffith, W. P. (2003). "Bicentenary of Four Platinum Group Metals: Osmium and iridium – events surrounding their discoveries". Platinum Metals Review 47 (4): 175–183.

[10] Hulett, G. A.; Berger, H. W. (1904). "VOLATILIZATION OF PLATINUM doi = 10.1021/ja02001a012". Journal of the American Chemical Society 26 (11): 1512. doi:10.1021/ja02001a012.

[11] Measurement, Astm Committee E.2.0. on Temperature (1993). "Platinum Type". Manual on the use of thermocouples in temperature measurement. ASTM International. ISBN 978-0-8031-1466-1.

[12] Kushner, Joseph B. (1940). "Modern rhodium plating". Metals and Alloys 11: 137–140.

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