Rh 45

Rhodium (Rh)

transition-metal

Period: 5 Group: 9 Block: s

Solid

Standard Atomic Weight

Electron configuration

[Kr] 5s¹ 4d⁸

Melting point

1963.85 °C (2237 K)

Boiling point

3694.85 °C (3968 K)

Density

1.240000e+4 kg/m³

Oxidation states

−3, −1, +1, +2, +3, +4, +5, +6, +7

Electronegativity (Pauling)

2.28

Ionization energy (1st)

Discovery year

1803

Atomic radius

135 pm

Details

Name origin Greek: rhodon (rose). Its salts give a rosy solution.

Discovery country England

Discoverers William Wollaston

Rhodium is a very rare platinum-group transition metal. It is chemically noble, hard, highly reflective, and most often encountered in nature alloyed with platinum, palladium, and other platinum-group elements. Its industrial importance is dominated by catalysis, especially control of nitrogen oxides in automotive exhaust. Rhodium also forms stable coordination compounds, commonly with Rh(I) and Rh(III), that are important in homogeneous catalysis and organometallic chemistry.

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.

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.

Read about Rhodium on Wikipedia

Images

Properties

Physical

Atomic radius (empirical) 135 pm

Covalent radius 142 pm

Van der Waals radius 195 pm

Metallic radius 125 pm

Density

Molar volume 0.0083 L/mol

Phase at STP solid

Melting point 1963.85 °C

Boiling point 3694.85 °C

Thermal conductivity 150 W/(m·K)

Specific heat capacity 0.243 J/(g·K)

Molar heat capacity 24.98 J/(mol·K)

Crystal structure fcc

Chemical

Electronegativity (Pauling) 2.28

Electronegativity (Allen) 1.56

Electron affinity

Ionization energy (1st)

Ionization energy (2nd)

Ionization energy (3rd)

Ionization energy (4th)

Ionization energy (5th)

Oxidation states −3, −1, +1, +2, +3, +4, +5, +6, +7

Valence electrons 9

Electron configuration

Electron configuration (semantic)

Thermodynamic

Heat of fusion 0.22490543 eV

Heat of vaporization 5.119967 eV

Heat of sublimation 5.762554 eV

Heat of atomization 5.762554 eV

Atomization enthalpy

Nuclear

Stable isotopes 1

Discovery year 1803

Abundance

Abundance (Earth's crust) 0.001 mg/kg

Reactivity

N/A

Crystal Structure

Lattice constant a 380 pm

Electronic Structure

Electrons per shell 2, 8, 18, 16, 1

Identifiers

CAS number 7440-16-6

Term symbol

InChI InChI=1S/Rh

InChI Key MHOVAHRLVXNVSD-UHFFFAOYSA-N

Electron Configuration Measured

Ion charge

Protons 45

Electrons 45

Charge Neutral

Configuration Rh: 4d⁸ 5s¹

[Kr] 4d⁸ 5s¹

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d⁸ 5s¹

Orbital diagram

↑↓

2/2

↑↓

2/2

↑↓

6/6

↑↓

2/2

↑↓

6/6

↑↓

2/2

↑↓

10/10

↑↓

6/6

↑

1/2 1↑

↑↓

↑

8/10 2↑

Total electrons: 45 Unpaired: 3

Atomic model

Protons 45

Neutrons 58

Electrons 45

Mass number 103

Stability Stable

Isotopes change neutron count, mass, and stability — not the electron configuration of a neutral atom.

Schematic atomic model, not to scale.

Atomic Fingerprint

Emission / Absorption Spectrum

Emission Visible: 380–750 nm

Isotope Distribution

Mass number	Atomic mass (u)	Natural abundance	Half-life
103 Stable	102.905498 ± 0.0000026	100.0000%	Stable

Measured

Phase / State

Solid 25 °C (298.15 K)

Reason: 1938.8 °C below melting point (1963.85 °C)

Melting point 1963.85 °C

Boiling point 3694.85 °C

Below melting by 1938.8 °C

0 K Current temperature: 25 °C 6000 K

Phase timeline

Schematic, not to scale

Solid

Liquid

Gas

Melting

Boiling

25°C

Solid

Liquid

Gas

Current

Phase transition points

Melting point Literature

1963.85 °C

Boiling point Literature

3694.85 °C

Current phase Calculated
Solid

Transition energies

Heat of fusion Literature

0.22490543 eV

Energy required to melt 1 mol at melting point

Heat of vaporization Literature

5.119967 eV

Energy required to vaporize 1 mol at boiling point

Heat of sublimation Literature

5.762554 eV

Energy required to sublime 1 mol at sublimation point

Density

Reference density Literature

1.240000e+4 kg/m³

At standard conditions

Current density Calculated

1.240000e+4 kg/m³

At standard conditions

Atomic Spectra

Showing 10 of 45 Atomic Spectra. Sorted by ion charge (ascending).

Lines Holdings ?

Ion	Charge	Total lines	Transition probabilities	Level designations
Rh I	0	468	111	443
Rh II	+1	34	0	31
Rh III	+2	73	0	0

NIST Lines Holdings →

Levels Holdings ?

Ion	Charge	Levels
Rh I	0	138
Rh II	+1	126
Rh III	+2	196
Rh IV	+3	2
Rh V	+4	2
Rh VI	+5	2
Rh VII	+6	2
Rh VIII	+7	2
Rh IX	+8	2
Rh X	+9	2

NIST Levels Holdings →

45 Rh 102.9055

Rhodium — Atomic Orbital Visualizer

[Kr]5s14d8

Energy levels 2 8 18 16 1

Oxidation states -3, -1, +1, +2, +3, +4, +5, +6, +7

HOMO 5s n=5 · l=0 · m=0

Rhodium — Atomic Orbital Visualizer Preview

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45 Rh 102.9055

Rhodium — Crystal Structure Visualizer

Face-Centered Cubic · Pearson cF4

Experimental

Pearson cF4

Coord. № 12

Packing 74.000%

Rhodium — Crystal Structure Visualizer Preview

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Ionic Radii

Charge	Coordination	Spin	Radius
+3	6	N/A	66.5 pm
+4	6	N/A	60 pm
+5	6	N/A	55.00000000000001 pm

Compounds

102.906 u

Rh+3

102.906 u

Rh+2

102.906 u

105.907 u

104.906 u

101.907 u

98.908 u

99.908 u

100.906 u

106.907 u

102.905 u

103.907 u

Isotopes (1)

	Mass number	Atomic mass (u)	Natural abundance	Half-life	Decay mode
	103 Stable	102.905498 ± 0.0000026	100.0000%	Stable	stable

103 Stable

Atomic mass (u) 102.905498 ± 0.0000026

Natural abundance 100.0000%

Half-life Stable

Decay mode

stable

Spectral Lines

Showing 50 of 186 Spectral Lines. Only spectral lines with measured intensity are shown by default.

Wavelength (nm)	Intensity	Ion stage	Type	Transition	Accuracy	Source
385.6513 nm	5900	Rh I	emission	4d8.(3F).5s a 2F → 4d8.(3F).5p z 2G*	Measured	NIST
437.4809 nm	4200	Rh I	emission	4d8.(3F).5s a 2F → 4d8.(3F).5p z 4G*	Measured	NIST
382.226 nm	3800	Rh I	emission	4d8.(3F).5s a 2F → 4d8.(3F).5p z 2F*	Measured	NIST
395.8856 nm	3800	Rh I	emission	4d8.(3F).5s a 2F → 4d8.(3F).5p z 2G*	Measured	NIST
421.1133 nm	3300	Rh I	emission	4d8.(3F).5s a 2F → 4d8.(3F).5p z 4F*	Measured	NIST
382.8478 nm	2300	Rh I	emission	4d8.(3P).5s a 4P → 4d8.(3P).5p z 4P*	Measured	NIST
413.5275 nm	2100	Rh I	emission	4d8.(3F).5s a 2F → 4d8.(3F).5p z 4F*	Measured	NIST
383.3884 nm	2000	Rh I	emission	4d8.(3F).5s a 2F → 4d8.(3F).5p z 2D*	Measured	NIST
393.4224 nm	2000	Rh I	emission	4d8.(3F).5s a 2F → 4d8.(3F).5p z 4G*	Measured	NIST
412.8886 nm	1500	Rh I	emission	4d8.(3F).5s a 2F → 4d8.(3F).5p z 2F*	Measured	NIST
380.6759 nm	1300	Rh I	emission	4d8.(3F).5s a 4F → 4d8.(3F).5p z 4D*	Measured	NIST
381.8186 nm	1300	Rh I	emission	4d8.(3P).5s a 4P → 4d8.(3P).5p z 4P*	Measured	NIST
412.1683 nm	1100	Rh I	emission	4d8.(3F).5s a 2F → 4d8.(3F).5p z 2D*	Measured	NIST
428.8702 nm	820	Rh I	emission	4d8.(3F).5s a 2F → 4d8.(3F).5p z 4G*	Measured	NIST
380.592 nm	760	Rh I	emission	4d8.(1D).5s b 2D → 8*	Measured	NIST
381.6474 nm	760	Rh I	emission	4d8.(1D).5s b 2D → 4d8.(1D).5p y 2F*	Measured	NIST
394.271 nm	590	Rh I	emission	4d8.(3P).5s a 4P → 4d8.(3P).5p z 4P*	Measured	NIST
408.278 nm	560	Rh I	emission	4d8.(3F).5s a 2F → 4d8.(3F).5p z 4F*	Measured	NIST
387.0018 nm	490	Rh I	emission	4d8.(1G).5s a 2G → 12*	Measured	NIST
381.5021 nm	470	Rh I	emission	4d8.(1G).5s a 2G → 13*	Measured	NIST
387.7346 nm	380	Rh I	emission	4d8.(3F).5s a 2F → 4d8.(3F).5p z 4F*	Measured	NIST
397.5313 nm	380	Rh I	emission	4d8.(1D).5s b 2D → 4*	Measured	NIST
399.6149 nm	380	Rh I	emission	4d8.(3P).5s a 2P → 4d8.(3P).5p y 4D*	Measured	NIST
419.6496 nm	330	Rh I	emission	4d8.(3P).5s a 4P → 4d8.(3F).5p z 2G*	Measured	NIST
392.2195 nm	240	Rh I	emission	4d9 a 2D → 4d8.(3F).5p z 4D*	Measured	NIST
398.4393 nm	240	Rh I	emission	4d8.(3P).5s a 4P → 4d8.(3P).5p z 4P*	Measured	NIST
399.5602 nm	240	Rh I	emission	4d8.(3P).5s a 4P → 4d8.(3P).5p z 4P*	Measured	NIST
415.4343 nm	240	Rh I	emission	4d7.5s2 b 4F → 4d8.(3P).5p y 4D*	Measured	NIST
559.9419 nm	160	Rh I	emission	4d8.(3P).5s a 4P → 4d8.(3F).5p z 4D*	Measured	NIST
467.5022 nm	150	Rh I	emission	4d8.(3F).5s a 2F → 4d8.(3F).5p z 4D*	Measured	NIST
409.7508 nm	140	Rh I	emission	4d8.(3P).5s a 4P → 4d8.(3P).5p z 4P*	Measured	NIST
456.8993 nm	130	Rh I	emission	4d8.(3P).5s a 4P → 4d8.(3F).5p z 4G*	Measured	NIST
535.4428 nm	130	Rh I	emission	4d8.(3F).5p z 2G* → 16	Measured	NIST
598.3575 nm	130	Rh I	emission	4d7.5s2 b 4F → 4d8.(3F).5p z 4F*	Measured	NIST
391.3508 nm	120	Rh I	emission	4d8.(3F).5s a 4F → 4d8.(3F).5p z 4D*	Measured	NIST
402.3139 nm	120	Rh I	emission	4d8.(1D).5s b 2D → 4d8.(1D).5p y 2P*	Measured	NIST
411.9679 nm	120	Rh I	emission	4d8.(1G).5s a 2G → 4d8.(1D).5p y 2F*	Measured	NIST
381.2462 nm	95	Rh I	emission	4d8.(1D).5s b 2D → 4d8.(3P).5p z 2S*	Measured	NIST
395.8233 nm	95	Rh I	emission	4d8.(3P).5s a 2P → 4d8.(1D).5p y 2P*	Measured	NIST
437.9911 nm	95	Rh I	emission	4d8.(3P).5s a 4P → 4d8.(3F).5p z 2D*	Measured	NIST
519.313 nm	95	Rh I	emission	4d8.(3F).5p z 4G* → 2	Measured	NIST
539.0433 nm	95	Rh I	emission	4d8.(3P).5s a 4P → 4d8.(3F).5p z 4D*	Measured	NIST
387.239 nm	70	Rh I	emission	4d9 a 2D → 4d8.(3F).5p z 4F*	Measured	NIST
388.8331 nm	70	Rh I	emission	4d8.(1D).5s b 2D → 4d8.(1D).5p y 2P*	Measured	NIST
407.758 nm	70	Rh I	emission	4d8.(1D).5s b 2D → 4d8.(3P).5p y 4D*	Measured	NIST
411.6329 nm	70	Rh I	emission	4d8.(1D).5s b 2D → 4*	Measured	NIST
420.6613 nm	70	Rh I	emission	4d9 a 2D → 4d8.(3F).5p z 4D*	Measured	NIST
429.6763 nm	70	Rh I	emission	4d8.(1D).5s b 2D → 4d8.(3P).5p y 4D*	Measured	NIST
474.5116 nm	70	Rh I	emission	4d8.(3F).5s a 2F → 4d8.(3F).5p z 4D*	Measured	NIST
509.064 nm	70	Rh I	emission	4d8.(3P).5s a 4P → 4d8.(3F).5p z 4D*	Measured	NIST

Extended Properties

Covalent Radii (Extended)

Covalent radius (Pyykkö)

Covalent radius (Pyykkö, double)

Covalent radius (Pyykkö, triple)

Van der Waals Radii

Batsanov

Alvarez

UFF

MM3

Atomic & Metallic Radii

Atomic radius (Rahm)

Metallic radius (C12)

Numbering Scales

Mendeleev

Pettifor

Glawe

Electronegativity Scales

Ghosh

Miedema

Gunnarsson–Lundqvist

Robles–Bartolotti

Polarizability & Dispersion

Dipole polarizability

Dipole polarizability (unc.)

C₆ (Gould–Bučko)

Chemical Affinity

Proton affinity

Gas basicity

Miedema Parameters

Miedema molar volume

Miedema electron density

Supply Risk & Economics

Production concentration

Relative supply risk

Reserve distribution

Political stability (top producer)

Political stability (top reserve)

Phase Transitions & Allotropes

Melting point	2236.15 K
Boiling point	3968.15 K

Oxidation State Categories

−1 extended

+2 extended

+6 extended

−3 extended

+4 extended

+3 main

+1 extended

+5 extended

+7 extended

Advanced Reference Data

Screening Constants (10)

n	Orbital	σ
1	s	0.9244
2	p	4.0596
2	s	11.8454
3	d	14.595
3	p	16.8456
3	s	16.5615
4	d	31.5576
4	p	27.8604
4	s	26.4184
5	s	38.3605

Crystal Radii Detail (3)

Charge	CN	r_crystal (pm)	Origin
3	VI	80.5	from r^3 vs V plots,
4	VI	74	from r^3 vs V plots, from metallic oxides,
5	VI	69

Isotope Decay Modes (72)

Isotope	Mode	Intensity
88	B+	—
89	B+	—
89	B+p	—
89	p	—
90	B+	100%
90	B+p	0.7%
91	B+	100%
91	B+p	1.3%
92	B+	100%
92	B+p	2%

X‑ray Scattering Factors (508)

Energy (eV)	f₁	f₂
10	—	1.17537
10.1617	—	1.24044
10.3261	—	1.30912
10.4931	—	1.3816
10.6628	—	1.4581
10.8353	—	1.53883
11.0106	—	1.62403
11.1886	—	1.71394
11.3696	—	1.80884
11.5535	—	1.90899

Additional Data

Estimated Crustal Abundance

The estimated element abundance in the earth's crust.

1×10-3 milligrams per kilogram

References (1)

[5] Rhodium https://education.jlab.org/itselemental/ele045.html

Estimated Oceanic Abundance

The estimated element abundance in the earth's oceans.

Not Applicable

References (1)

[5] Rhodium https://education.jlab.org/itselemental/ele045.html

Sources

Sources of this element.

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.

References (1)

[6] Rhodium https://periodic.lanl.gov/45.shtml

References

(9)

1 PubChem

Data deposited in or computed by PubChem

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2 Atomic Mass Data Center (AMDC), International Atomic Energy Agency (IAEA)

The half-life and atomic mass data was provided by the Atomic Mass Data Center at the International Atomic Energy Agency.

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3 IUPAC Commission on Isotopic Abundances and Atomic Weights (CIAAW)

Rhodium

Element data are cited from the Atomic weights of the elements (an IUPAC Technical Report). The IUPAC periodic table of elements can be found at https://iupac.org/what-we-do/periodic-table-of-elements/. Additional information can be found within IUPAC publication doi:10.1515/pac-2015-0703 Copyright © 2020 International Union of Pure and Applied Chemistry.

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4 IUPAC Periodic Table of the Elements and Isotopes (IPTEI)

The information are cited from Pure Appl. Chem. 2018; 90(12): 1833-2092, https://doi.org/10.1515/pac-2015-0703.

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License note: 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.

5 Jefferson Lab, U.S. Department of Energy

Rhodium

Thomas Jefferson National Accelerator Facility (Jefferson Lab) is one of 17 national laboratories funded by the U.S. Department of Energy. The lab's primary mission is to conduct basic research of the atom's nucleus using the lab's unique particle accelerator, known as the Continuous Electron Beam Accelerator Facility (CEBAF). For more information visit https://www.jlab.org/

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License note: Please see citation and linking information: https://education.jlab.org/faq/index.html

6 Los Alamos National Laboratory, U.S. Department of Energy

Rhodium

The periodic table at the LANL (Los Alamos National Laboratory) contains basic element information together with the history, source, properties, use, handling and more. The provenance data may be found from the link under the source name.

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7 NIST Physical Measurement Laboratory

Rhodium

The periodic table contains NIST's critically-evaluated data on atomic properties of the elements. The provenance data that include data for atomic spectroscopy, X-ray and gamma ray, radiation dosimetry, nuclear physics, and condensed matter physics may be found from the link under the source name. Ref: https://www.nist.gov/pml/atomic-spectra-database

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8 PubChem Elements

Rhodium

This section provides all form of data related to element Rhodium.

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9 PubChem Elements

Rhodium

The element property data was retrieved from publications.

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Last updated: May 1, 2026

Data verified: May 12, 2026

Content is reviewed against latest scientific data.