Rhodium (Rh): Electron Configuration, Properties and Uses
Rhodium (Rh): Electron Configuration, Properties and Uses
Electron configuration [Kr] 5s1 4d8 · group 9 · period 5 · Ar 102.91
Rhodium data
- Atomic number
- 45
- Relative atomic mass
- 102.91
- Group
- 9
- Period
- 5
- Block
- d
- Category
- Transition metal
- Electron configuration
- [Kr] 5s1 4d8
- Full configuration
- 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s1 4d8
- Electrons per shell
- 2, 8, 18, 16, 1 (K L M N O)
- Valence electrons
- 9
- Electronegativity (Pauling)
- 2.28
- First ionisation energy
- 7.459 eV
- Atomic radius (van der Waals)
- 195 pm
- State at room temperature
- Solid
- Melting point
- 1964 °C
- Boiling point
- 3695 °C
- Density
- 12.4 g/cm³
- Common oxidation states
- +3
- Discovered
- 1803
Source: PubChem (NIH, accessed 13 Nov 2026); atomic mass: IUPAC standard atomic weight.
Electron shell diagram
K 2 · L 8 · M 18 · N 16 · O 1
Orbital diagram (outer electrons)
About rhodium
Rhodium is a chemical element with the symbol Rh and atomic number 45. It is a transition metal in group 9, period 5, d-block. The element was discovered in 1803. Rhodium is a solid at room temperature, melting at 1964 °C and boiling at 3695 °C.
Rhodium electron configuration
The electron configuration of rhodium is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s1 4d8, or in short [Kr] 5s1 4d8. Its electrons occupy 5 shells: K = 2, L = 8, M = 18, N = 16, O = 1. For transition metals, valence electrons are counted from the 5s and 4d subshells: 1 + 8 = 9, matching group 9. This is an exception to the Aufbau rule: the usual filling order predicts [Kr] 5s2 4d7, but the 5s and 4d subshells are so close in energy that electrons occupy 4d. When it forms cations, electrons leave the outermost subshell first: Rh3+ = [Kr] 4d6.
Filling order: 1s2(2) → 2s2(4) → 2p6(10) → 3s2(12) → 3p6(18) → 4s2(20) → 3d10(30) → 4p6(36) → 5s1(37) → 4d8(45)
Uses of rhodium
The main uses of rhodium include vehicle catalytic converters, plating jewellery and mirrors, and hydroformylation catalysts. For research and analysis you can browse rhodium compounds in the AMI Scientific catalogue.
Safety
As a solid metal, rhodium is not especially hazardous. Fine powder can burn, and its compounds should be handled according to their SDS. Always read the safety data sheet (SDS) before working with a chemical.
Other elements in group 9
Frequently asked questions
What is the electron configuration of rhodium?
The electron configuration of rhodium (Rh, atomic number 45) is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s1 4d8, or [Kr] 5s1 4d8 in short. By shell: 2, 8, 18, 16, 1.
How many valence electrons does rhodium have?
Rhodium has 9 valence electrons.
Which group and period is rhodium in?
Rhodium is in group 9, period 5, d-block.
What is the atomic mass of rhodium?
The relative atomic mass of rhodium is 102.91. Use it to calculate molar mass with the molar mass calculator.
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