ElementsWhat is rhodium?
Rhodium is a silvery-white, very reflective and very rare metal. It is among the most costly of all metals.
What is rhodium used for?
Catalytic converters that clean car exhaust, plating on white gold jewellery, and mirrors.
Where the name comes from
From the Greek word rhodon, rose, for the rose colour of its salts.
Key facts
- Symbol
- Rh
- Atomic number
- 45
- Atomic mass
- 102.9055 u
- Family
- Transition metal
- Period
- 5
- Group
- 9
- Block
- d
- State at room temperature
- Solid
- Melting point
- 1,964 °C (2,237 K, 3,567 °F)
- Boiling point
- 3,695 °C (3,968 K, 6,683 °F)
- Density
- 12.4 g/cm³
- Electrons per shell
- 2, 8, 18, 16, 1
- Electron configuration
- [Kr]5s1 4d8
- Common oxidation states
- +3
- Electronegativity (Pauling)
- 2.28
- First ionisation energy
- 7.459 eV
- Electron affinity
- 1.137 eV
- Atomic radius (van der Waals)
- 195 pm
- Discovered
- 1803
Place in the periodic table
Rhodium is element number 45. It sits in period 5 (row 5) of the periodic table, in group 9 (column 9), and belongs to the d-block. Just before it comes ruthenium (44), and just after it comes palladium (46). In the same column, cobalt is above it and iridium is below it. Elements in one column tend to behave alike.
Family: Transition metals.
Physical properties
At room temperature rhodium is a solid. It melts at 1,964 °C and boils at 3,695 °C, so it stays liquid over a range of 1,731 degrees. Its density is 12.4 grams per cubic centimetre, so a one-litre block would weigh about 12.4 kilograms. By density it ranks 17th among the 96 elements with a measured value.
Inside the atom
An atom of rhodium has 45 protons in its nucleus and, when neutral, 45 electrons around it. The electrons are arranged in 5 shells: 2, 8, 18, 16, 1. The outermost shell holds 1 electron. Written in full, the electron configuration is [Kr]5s1 4d8.
Its electronegativity on the Pauling scale is 2.28. This number shows how strongly an atom pulls shared electrons towards itself: fluorine, the strongest, is 3.98. Removing one electron from an atom takes 7.459 electronvolts (about 720 kilojoules per mole). One mole of rhodium weighs 102.9055 grams, so a single gram contains about 5.85 × 1021 atoms.
The ring picture is a simple model that only counts the electrons in each shell. Real atoms do not look like this.
Next steps
- Work out the weight of a compound that contains rhodium with the molar mass calculator.
- Compare it with every other element in the sortable list.
- Test yourself with the symbol quiz.
Figures on this page are from PubChem (U.S. National Library of Medicine), as downloaded on 11 November 2026. See About and data sources.