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Rhodium

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Rhodium

Atomic Mass	102.90550
Electron Configuration	[Kr]5s14d8
Oxidation States	+3
Year Discovered	1803

Rhodium

Atomic Mass	102.90550
Electron Configuration	[Kr]5s14d8
Oxidation States	+3
Year Discovered	1803

Identifiers

Element Name	Rhodium
Element Symbol	Rh
InChI	InChI=1S/Rh
InChIKey	MHOVAHRLVXNVSD-UHFFFAOYSA-N

Properties

Atomic Weight	102.905 49(2) 102.90550 102.9 102.90550(2)
Electron Configuration	[Kr]5s¹4d⁸
Atomic Radius	Van der Waals Atomic Radius :195 pm (Van der Waals) Empirical Atomic Radius :135pm (Empirical) Covalent Atomic Radius :142(7) pm (Covalent)
Oxidation States	+3 6, 5, 4, 3, 2, 1, -1, -3 (an amphoteric oxide)
Ground Level	⁴F_9/2
Ionization Energy	7.459 eV 7.45890 ± 0.00005 eV
Electronegativity	Pauling Scale Electronegativity :2.28(Pauling Scale) Allen Scale Electronegativity :1.56(Allen Scale)
Electron Affinity	1.137eV 1.68eV
Atomic Spectra	Lines Holdings Levels Holdings
Physical Description	Solid
Element Classification	Metal
Element Period Number	5
Element Group Number	9
Density	12.4 grams per cubic centimeter
Melting Point	2237 K (1964°C or 3567°F) 1964°C
Boiling Point	3968 K (3695°C or 6683°F) 3695°C
Estimated Crustal Abundance	1×10^-3 milligrams per kilogram
Estimated Oceanic Abundance	Not Applicable

History

The name derives from the Greek rhodon for rose because of the rose color of dilute solutions of its salts. It was discovered by the English chemist and physicist William Hyde Wollaston in 1803 in a crude platinum ore.

Rhodium was discovered by William Hyde Wollaston, an English chemist, in 1803 shortly after his discovery of the element palladium. He obtained rhodium from a sample of platinum ore that was obtained from South America. After removing the platinum and palladium from the sample, he was left with a dark red powder. The powder turned out to be sodium rhodium chloride (Na3RhCl6·12H2O). Wollaston obtained rhodium from the powder by treating it with hydrogen gas (H2). Rhodium tends to occur along with deposits of platinum and is primarily obtained as a byproduct of mining and refining platinum. Rhodium is also obtained as a byproduct of the nickel mining operation in the Sudbury region of Ontario, Canada.

From the Greek word rhodon, rose. Wollaston discovered rhodium between 1803 and 1804 in crude platinum ore he presumably obtained from South America.

Historical Atomic Weights

Year	Atomic Weight (uncertainty) [u]	Reference
2017	102.905 49(2)	https://doi.org/10.1515/pac-2019-0603
1995	102.905 50(2)	https://doi.org/10.1351/pac199668122339
1985	102.905 50(3)	https://doi.org/10.1351/pac198658121677
1969	102.9055(1)	https://doi.org/10.1351/pac197021010091
1961	102.905	https://doi.org/10.1021/ja00881a001
1925	102.91	https://doi.org/10.1039/CT9252700913
1909	102.9	https://doi.org/10.1021/ja01931a001
1902	103.0	https://doi.org/10.1007/BF01370337

Historical Isotopic Abundances

Year	Isotope	Abundance (uncertainty)	Reference
1975, ¹⁰³Rh, 1, doi:10.1351/pac197647010075

Description

The metal is silvery white and at red heat slowly changes in air to the resquioxide. At higher temperatures it converts back to the element. Rhodium has a higher melting point and lower density than platinum. It is highly reflective, hard, and durable.

Users

Rhodium is used to make electrical contacts, as jewelry and in catalytic converters, but is most frequently used as an alloying agent in other materials, such as platinum and palladium. These alloys are used to make such things as furnace coils, electrodes for aircraft spark plugs and laboratory crucibles.

Rhodium's primary use is as an alloying agent to harden platinum and palladium. Such alloys are used for furnace windings, thermocoupling elements, bushings for glass fiber production, electrodes for aircraft spark plugs, and laboratory crucibles. It is useful as an electrical contact material as it has a low electrical resistance, a low and stable contact resistance, and is highly resistant to corrosion. Plated rhodium, produced by electroplating or evaporation, is exceptionally hard and is used for optical instruments. Rhodium is also used for jewelry, for decoration, and as a catalyst.

Sources

Rhodium occurs natively with other platinum metals in river sands of the Urals and in North and South America. It is also found with other platinum metals in the copper-nickel sulfide area of the Sudbury, Ontario region. Although the quantity occurring there is very small, the large tonnages of nickel processed make the recovery commercially feasible. The annual world production of rhodium is only 7 or 8 tons.

Compounds

See more information at the Rhodium compound page.

Element Forms

CID	Name	Formula	SMILES	Molecular Weight
23948	rhodium	Rh	[Rh]	102.9055
167511	rhodium(3+)	Rh+3	[Rh+3]	102.9055
185497	rhodium(2+)	Rh+2	[Rh+2]	102.9055
105129	rhodium-106	Rh	[106Rh]	105.90729
167192	rhodium-105	Rh	[105Rh]	104.90569
167420	rhodium-102	Rh	[102Rh]	101.90683
177676	rhodium-99	Rh	[99Rh]	98.9081
177677	rhodium-100	Rh	[100Rh]	99.9081
178191	rhodium-101	Rh	[101Rh]	100.90616
177637	rhodium-107	Rh	[107Rh]	106.9067
10176103	rhodium-103	Rh	[103Rh]	102.90549
9877348	rhodium-104	Rh	[104Rh]	103.90665

Handling And Storage

Exposure to rhodium (metal fume and dust, as Rh) should not exceed 1 mg/m^3 (8-hour time-weighted average, 40-hour week).

Isotopes

Stable Isotope Count	1

Isotopes in Medicine

The beta particles of 105Rh (with a half-life of about 35 h) are used in target radiotherapy to kill cancer cells or cause cancer cell sterilization [334]. The gamma rays from 105Rh enable in vivo tracking during radiotherapy [334]. 105Rh has been used in the treatment of bone pain (Fig. IUPAC.45.1) [334], [337].

Ocular brachytherapy currently is performed using 125I (with a half-life of about 59 days) or 106Rh (with a half-life of about 30 s) seeds [338]. Brachytherapy can allow a good spatial dose distribution over the ocular tumor with lower radiation on adjacent tissues. In the case of irradiation of the eyeball with 106Rh, 80 percent of the dose has been absorbed within a depth of 5.2 mm and 90 percent has been absorbed within 7.2 mm (Fig. IUPAC.45.2). This limits the application of 106Rh; however, when 106Rh can be used, the radiation dose can be lower, which is preferred.

Fig. IUPAC.45.1: Bone cancer cells that have been pap stained and magnified to 400 times. The beta particles and gamma rays of ¹⁰⁵Rh are used, respectively, in radiotherapy to kill cancer cells and for in vivo tracking during radiotherapy [339]. (Photo Source: National Cancer Institute at the National Institutes of Health).

Fig. IUPAC.45.2: Variation in absorbed dose of ¹⁰⁶Rh as a function of tissue depth in ocular brachytherapy (modified from [338]).

[334] A. R. Ketring, G. J. Ehrhardt, M. F. Embree, T. T. Tyler, J. A. Gawenis, S. S. Jurisson, H. P. Engelbrecht, C. J. Smith, C. S. Cutler. Alasbimn J.5 (19), (2003).

[337] Trace Sciences International Inc. Ruthenium Isotopes, Trace Sciences International Inc (2014), Feb. 26; http://www.tracesciences.com/ru.htm.

[338] A. P. Mourão, T. P. R. D. Campos. Radiol. Bras.42, 43 (2009).

[339] A. Ando, I. Ando, N. Tonami, S. Kinuya, N. Okamoto, M. Sugimoto, N. Fukuda, S. Matsumoto. Appl. Radiat. Isotopes52 (2), 211 (2000).

Isotope Mass and Abundance

Isotope	Atomic Mass (uncertainty) [u]	Abundance (uncertainty)
^103Rh	102.905 49(2)	1

Isotope	Atomic Mass (uncertainty) [u]	Abundance (uncertainty)
¹⁰³Rh	102.9054980(26)	1

Atomic Mass, Half Life, and Decay

Nuclide	Atomic Mass and Uncertainty [u]	Half Life and Uncertainty	Discovery Year	Decay Modes, Intensities and Uncertainties [%]
⁸⁸Rh	87.960429 ± 0.000429 [Estimated]	1 ms [Estimated]		β⁺ ?
⁸⁹Rh	88.950992 ± 0.000387 [Estimated]	Not-specified <120ns		β⁺ ?; β⁺p ?; p ?
⁹⁰Rh	89.944569 ± 0.000215 [Estimated]	29 ms ± 3	1994	β⁺=100%; β⁺p<0.7%
⁹⁰Rh^m	89.944569 ± 0.000215 [Estimated]	0.56 s ± 0.02	2001	β⁺=100%; β⁺p=9.6±1%
⁹¹Rh	90.937123 ± 0.00032 [Estimated]	1.47 s ± 0.22	1994	β⁺=100%; β⁺p=1.3±0.5%
⁹¹Rh^m	90.937123 ± 0.00032 [Estimated]	1.8 s [Estimated]	2004	β⁺ ?; IT ?; β⁺p ?
⁹²Rh	91.932367692 ± 0.0000047	5.61 s ± 0.08	1994	β⁺=100%; β⁺p=2.05±0.7%
⁹²Rh^m	91.932367692 ± 0.0000047	3.18 s ± 0.22	2004	β⁺=100%; β⁺p=1.7±0.3%
⁹²Rhⁿ	91.932367692 ± 0.0000047	232 ns ± 15	2017	IT=100%
⁹³Rh	92.925912778 ± 0.000002821	13.9 s ± 1.6	1994	β⁺=100%
⁹⁴Rh	93.921730450 ± 0.000003627	70.6 s ± 0.6	1979	β⁺=100%; β⁺p=1.8±0.5%
⁹⁴Rh^m	93.921730450 ± 0.000003627	480 ns ± 30	2004	IT=100%
⁹⁴Rhⁿ	93.921730450 ± 0.000003627	25.8 s ± 0.2	1973	β⁺=100%
⁹⁵Rh	94.915897893 ± 0.000004171	5.02 m ± 0.10	1967	β⁺=100%
⁹⁵Rh^m	94.915897893 ± 0.000004171	1.96 m ± 0.04	1974	IT=88±0.5%; β⁺=12±0.5%
⁹⁶Rh	95.914451705 ± 0.000010737	9.90 m ± 0.10	1967	β⁺=100%
⁹⁶Rh^m	95.914451705 ± 0.000010737	1.51 m ± 0.02	1966	IT=60±0.5%; β⁺=40±0.5%
⁹⁷Rh	96.911327872 ± 0.000038071	30.7 m ± 0.6	1955	β⁺=100%
⁹⁷Rh^m	96.911327872 ± 0.000038071	46.2 m ± 1.6	1971	β⁺=94.4±0.6%; IT=5.6±0.6%
⁹⁸Rh	97.910707734 ± 0.000012782	8.72 m ± 0.12	1955	β⁺=100%
⁹⁸Rh^m	97.910707734 ± 0.000012782	3.6 m ± 0.2	1966	IT=89±0.5%; β⁺=11±0.5%
⁹⁹Rh	98.908121241 ± 0.000020881	16.1 d ± 0.2	1952	β⁺=100%
⁹⁹Rh^m	98.908121241 ± 0.000020881	4.7 h ± 0.1	1952	β⁺≈100%; IT ?
¹⁰⁰Rh	99.908114147 ± 0.000019458	20.8 h ± 0.1	1948	β⁺=100%; ε=95.1±0.5%; e⁺=4.9±0.5%
¹⁰⁰Rh^m	99.908114147 ± 0.000019458	214.0 ns ± 2.0	1965	IT=100%
¹⁰⁰Rhⁿ	99.908114147 ± 0.000019458	4.6 m ± 0.2	1973	IT≈98.3%; β⁺≈1.7%
¹⁰⁰Rh^p	99.908114147 ± 0.000019458	130 ns ± 10	1984	IT=100%
¹⁰¹Rh	100.906158903 ± 0.00000627	4.07 y ± 0.05	1948	ε=100%
¹⁰¹Rh^m	100.906158903 ± 0.00000627	4.343 d ± 0.010	1944	ε=92.80±2.5%; IT=7.20±2.5%
¹⁰²Rh	101.906834282 ± 0.00000688	207.0 d ± 1.5	1941	β⁺=78±0.5%; β^-=22±0.5%
¹⁰²Rh^m	101.906834282 ± 0.00000688	3.742 y ± 0.010	1962	β⁺≈100%; IT=0.233±2.4%
¹⁰³Rh	102.905494081 ± 0.00000247	Stable	1934	IS=100%
¹⁰³Rh^m	102.905494081 ± 0.00000247	56.114 m ± 0.009	1943	IT=100%
¹⁰⁴Rh	103.906645309 ± 0.000002471	42.3 s ± 0.4	1939	β^-=99.55±1%; β⁺=0.45±1%
¹⁰⁴Rh^m	103.906645309 ± 0.000002471	4.34 m ± 0.03	1939	IT=99.87±0.1%; β^-=0.13±0.1%
¹⁰⁵Rh	104.905687787 ± 0.000002685	35.341 h ± 0.019	1945	β^-=100%
¹⁰⁵Rh^m	104.905687787 ± 0.000002685	42.8 s ± 0.3	1950	IT=100%
¹⁰⁶Rh	105.907285879 ± 0.000005786	30.07 s ± 0.35	1947	β^-=100%
¹⁰⁶Rh^m	105.907285879 ± 0.000005786	131 m ± 2	1955	β^-=100%
¹⁰⁷Rh	106.906747975 ± 0.000012937	21.7 m ± 0.4	1951	β^-=100%
¹⁰⁷Rh^m	106.906747975 ± 0.000012937	>10 us	1986	IT=100%
¹⁰⁸Rh	107.908715304 ± 0.000015026	16.8 s ± 0.5	1955	β^-=100%
¹⁰⁸Rh^m	107.908715304 ± 0.000015026	6.0 m ± 0.3	1969	β^-=100%
¹⁰⁹Rh	108.908749555 ± 0.000004336	80.8 s ± 0.7	1972	β^-=100%
¹⁰⁹Rh^m	108.908749555 ± 0.000004336	1.66 us ± 0.04	1987	IT=100%
¹¹⁰Rh	109.911079745 ± 0.000019114	3.35 s ± 0.12	1963	β^-=100%
¹¹⁰Rh^m	109.911079745 ± 0.000019114	28.5 s ± 1.3	1969	β^-=100%
¹¹¹Rh	110.911643164 ± 0.000007356	11 s ± 1	1975	β^-=100%
¹¹²Rh	111.914405199 ± 0.000047327	3.4 s ± 0.4	1972	β^-=100%
¹¹²Rh^m	111.914405199 ± 0.000047327	6.73 s ± 0.15	1987	β^-=100%
¹¹³Rh	112.915440212 ± 0.000007656	2.80 s ± 0.12	1971	β^-=100%
¹¹⁴Rh	113.918721680 ± 0.000076824	1.85 s ± 0.05	1988	β^-=100%
¹¹⁴Rh^m	113.918721680 ± 0.000076824	1.85 s ± 0.05	1987	β^-=100%
¹¹⁵Rh	114.920311649 ± 0.000007857	1.03 s ± 3	1988	β^-=100%; β^-n ?
¹¹⁶Rh	115.924062060 ± 0.000079261	685 ms ± 39	1970	β^-=100%; β^-n<2.1%
¹¹⁶Rh^m	115.924062060 ± 0.000079261	570 ms ± 50	1987	β^-=100%; β^-n<2.1%
¹¹⁷Rh	116.926036291 ± 0.000009548	421 ms ± 30	1991	β^-=100%; β^-n<7.6%
¹¹⁷Rh^m	116.926036291 ± 0.000009548	138 ns ± 17	2013	IT=100%
¹¹⁸Rh	117.930341116 ± 0.000026018	282 ms ± 9	1994	β^-=100%; β^-n=3.1±1.4%
¹¹⁸Rh^m	117.930341116 ± 0.000026018	310 ms ± 30	1994	β^-≈100%; IT ?; β^-n=3.1±1.4%
¹¹⁹Rh	118.932556951 ± 0.00001	190 ms ± 6	1994	β^-=100%; β^-n=6.4±1.6%
¹²⁰Rh	119.937069 ± 0.000215 [Estimated]	129.6 ms ± 4.2	1994	β^-=100%; β^-n<9.3%; β^-2n ?
¹²⁰Rh^m	119.937069 ± 0.000215 [Estimated]	295 ns ± 16	2012	IT=100%
¹²¹Rh	120.939613000 ± 0.000665	74 ms ± 4	1994	β^-=100%; β^-n>11%
¹²²Rh	121.944305 ± 0.000322 [Estimated]	51 ms ± 6	1997	β^-=100%; β^-n<3.9%; β^-2n ?
¹²²Rh^m	121.944305 ± 0.000322 [Estimated]	830 ns ± 120	2012	IT=100%
¹²³Rh	122.947192 ± 0.000429 [Estimated]	42 ms ± 4	2010	β^-=100%; β^-n>24%; β^-2n ?
¹²⁴Rh	123.952002 ± 0.000429 [Estimated]	30 ms ± 2	2010	β^-=100%; β^-n<31%; β^-2n ?
¹²⁵Rh	124.955094 ± 0.000537 [Estimated]	26.5 ms ± 2.0	2010	β^-=100%; β^-n ?; β^-2n ?
¹²⁶Rh	125.960064 ± 0.000537 [Estimated]	19 ms ± 3	2010	β^-=100%; β^-n ?; β^-2n ?
¹²⁷Rh	126.963789 ± 0.000644 [Estimated]	28 ms ± 14	2015	β^-=100%; β^-n ?; β^-2n ?
¹²⁸Rh	127.970649 ± 0.000322 [Estimated]	8 ms >550ns [Estimated]	2018	β^- ?; β^-n ?; β^-2n ?

Information Sources

1. PubChem
https://pubchem.ncbi.nlm.nih.gov
2. Atomic Mass Data Center (AMDC), International Atomic Energy Agency (IAEA)
LICENSE
https://www-nds.iaea.org/disclaimer.html

Rh
https://www-nds.iaea.org/amdc/
3. IUPAC Commission on Isotopic Abundances and Atomic Weights (CIAAW)
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http://www.ciaaw.org/bylaws.htm

Rhodium
https://www.ciaaw.org/rhodium.htm
4. Jefferson Lab, U.S. Department of Energy
LICENSE
Please see citation and linking information https https://www.jlab.org/privacy-and-security-notice

Rhodium
https://education.jlab.org/itselemental/ele045.html
5. Los Alamos National Laboratory, U.S. Department of Energy
LICENSE
https://about.lanl.gov/lanl-resources/web-policies/

Rhodium
https://periodic.lanl.gov/45.shtml
6. NIST Physical Measurement Laboratory
LICENSE
https://www.nist.gov/pml/database-disclaimer

Rhodium
https://physics.nist.gov/cgi-bin/Elements/elInfo.pl?element=45
7. IUPAC Periodic Table of the Elements and Isotopes (IPTEI)
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Copyright (c) 2020 International Union of Pure and Applied Chemistry. The International Union of Pure and Applied Chemistry (IUPAC) contribution within Pubchem is provided under a CC-BY-NC-ND 4.0 license, unless otherwise stated.
https://creativecommons.org/licenses/by-nc-nd/4.0/
https://doi.org/10.1515/pac-2015-0703
8. PubChem Elements
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https://www.nlm.nih.gov/copyright.html

Rhodium

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