Rhodium is a corrosion-resistant platinum-group metal valued for catalysis. It helps reduce nitrogen oxides in vehicle exhaust and is used in other chemical processes. Its roles in reflective coatings and electrical contacts also show how surface properties influence an engineered component's performance.
FROM ELEMENT TO APPLICATION
AN ELEMENT IN CONTEXT
How does a rhodium catalyst reduce nitrogen oxides without simply storing them?
Rhodium-containing supported catalyst
FOLLOW THIS RELATIONSHIP
Bring exhaust to catalytic sites
Exhaust encounters a supported rhodium-containing material. The accessible surface and its surrounding chemical environment matter to the reactions that can occur.
Explore the model (optional)
RhFORM → INTERACTION → CONSEQUENCE
Follow the explanation in either direction. These are authored steps, not a physical clock.
Optional: check your understanding
USE THE EXPLANATION
Which observation would distinguish conversion from simple pollutant storage?
Atomic identity, reference properties and structure models
INTERACTIVE 3D45 visible sites
An electron censusDrag to rotate · scroll or pinch to zoom
[Kr] 4d8 5s1. Grouping electrons by principal shell connects the neutral-atom configuration to periodic-table patterns.
What this representation means
A three-dimensional counting diagram. Dots are count markers, not measured electron positions; spherical placement and spacing are arbitrary. There are no electron trajectories here. Orbitals describe quantum states.
William Hyde Wollaston found rhodium in 1803 while separating the constituents of platinum . A rose-colored salt gave the element its name, and further work produced the metal. Its history shows why color can be a clue without being the final identification: the observed salt was a compound, while rhodium was the element shared by that compound and the subsequently obtained metallic material.
1803
Rose-colored compound separated
Wollaston recognized a distinctive salt in platinum-ore chemistry.
1803
Metal obtained
Further chemical work yielded the newly identified rhodium.
Rhodium is associated with platinum-group resources and is also recovered through copper and nickel processing. It is not ordinarily mined as a conveniently separate pure substance. Its occurrence connects extraction to chemical separation, because neighboring valuable metals can enter the same ore-processing and stream.
Rhodium is a hard, reflective, corrosion-resistant metal. At a surface, its significance is different: it helps reactions proceed through accessible pathways. Surface activity and bulk reflectivity should be considered separately. A thin coating, dispersed catalyst, and solid metal specimen can therefore serve very different purposes.
Each section links its supporting references. Descriptions and diagrams were authored for this atlas. Source checks completed. Source checks dated 2026-09-06.
CITE THIS PAGE
Family labels and the group-3 layout are teaching conventions. A table position does not establish an unknown bulk property. Electronic configurations refer to neutral atoms; ions and material environments require their own account.
Read each reference property together with its units, conditions and the reference information below.
Not yet recorded: electron affinity, second ionization energy, ground-state term symbol, van der waals radius, thermal conductivity, specific heat capacity, electrical resistivity, crystal structure, lattice parameter a, space group, abundance in seawater, abundance in the universe, annual production, supply-risk listing, hazard classification, biological role, cas registry number, pubchem cid, wikidata item. These families are declared and awaiting an ingestion run against the source each names; they are listed here rather than shown as empty rows.
Physical
Intended reference: CRC Handbook of Chemistry and Physics · CRC Press
Phase at 20 °C
solid
293.15 K, 101.325 kPa
Melting point in K
2237 K
at standard pressure unless noted
Boiling point in K
3968 K
101.325 kPa
Density in g/cm³
12.41 g/cm³
solids and liquids at 293 K; gases at 273 K and 101.325 kPa
Atomic and electronic
Intended reference: Pauling electronegativity scale · Widely tabulated; original in The Nature of the Chemical Bond
Electronegativity in Pauling
2.28 Pauling
Pauling scale
First ionization energy in kJ/mol
719.7 kJ/mol
gas-phase neutral atom, ground state
Covalent radius in pm
142 pm
single-bond covalent radius
Common oxidation states
+3
states met in ordinary compounds; not exhaustive
Occurrence and identity
Intended reference: CRC Handbook of Chemistry and Physics · CRC Press
Abundance in the crust in mg/kg
0.001 mg/kg
upper continental crust, mass fraction
Has stable isotopes
Yesderived
Discovery year in CE
1803 CEderived
WHERE IT SITS AMONG ITS NEIGHBORS
Electronegativity across period 5
Rh 2.28 Pauling · Rhodium
Electronegativity across period 5. Exact values.
Rb
0.82
Sr
0.95
Y
1.22
Zr
1.33
Nb
1.6
Mo
2.16
Tc
1.9
Ru
2.2
Rh
2.28
Pd
2.2
Ag
1.93
Cd
1.69
In
1.78
Sn
1.96
Sb
2.05
Te
2.1
I
2.66
Xe
2.6
Electronegativity down group 9
Rh 2.28 Pauling · Rhodium
Electronegativity down group 9. Exact values.
Co
1.88
Rh
2.28
Ir
2.2
The trend uses the same reference-property values as the periodic table. Elements with no recorded value are left out of the line rather than drawn at zero.
