Rhodium (Rh)
Transition metal
Rhodium is often the most expensive metal on Earth — a brilliant, untarnishable platinum-group metal. Most of it goes into catalytic converters, where it scrubs nitrogen oxides from car exhaust.
Position on the periodic table
Atomic properties
| Atomic number | 45 |
|---|---|
| Atomic mass | 102.906 amu |
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s1 4d8 |
| Noble gas shorthand | [Kr] 4d8 5s1 |
| Electrons per shell | 2, 8, 18, 16, 1 |
| Valence electrons (outer shell) | 1 |
| Common oxidation states | +3 |
| Electronegativity (Pauling) | 2.28 |
| Covalent radius (approx.) | 142 pm |
| First ionization energy | 719.7 kJ/mol |
| Electron affinity | 110.3 kJ/mol |
Physical properties
| State at 25 °C | Solid |
|---|---|
| Density | 12.41 g/cm³ |
| Melting point | 1963.8 °C (2237 K) |
| Boiling point | 3694.8 °C (3968 K) |
| Appearance | silvery white metallic |
| Radioactive | No |
| Origin | Occurs naturally |
Electron configuration of rhodium
Rhodium's ground-state electron configuration is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s1 4d8, usually shortened to [Kr] 4d8 5s1. Its electrons occupy 5 shells (2, 8, 18, 16, 1), placing it in period 5 of the d-block. Explore it interactively in the electron configuration calculator.
Uses of rhodium
- Catalytic converters (NOx reduction)
- Jewellery plating
- Aircraft spark-plug alloys
- Glass-fibre production equipment
Biological role: None known.
Occurrence: Among the rarest non-radioactive elements; a by-product of platinum and nickel mining.
Common compounds of rhodium
RhCl3
Rhodium(III) chloride
History and discovery
Discovered: 1803 — William Hyde Wollaston. Name origin: From Greek rhodon, rose — its salts form rose-red solutions.
William Hyde Wollaston discovered rhodium in 1803 shortly after finding palladium.
Safety notes
Metallic rhodium is inert and safe; its soluble compounds are treated as toxic.
Educational context only — always follow your school's laboratory rules and never handle chemicals without proper supervision. See our disclaimer.
Practice questions
Quick practice: Rhodium
1. What is the chemical symbol of Rhodium?
2. What is the atomic number of Rhodium?
3. Which category does Rhodium belong to?
4. What is the state of Rhodium at room temperature?
5. Which period of the periodic table is Rhodium in?
Rhodium FAQs
What is the atomic number of rhodium?
Rhodium's atomic number is 45 — every rhodium atom has 45 protons in its nucleus.
What is the symbol for rhodium?
Rh. From Greek rhodon, rose — its salts form rose-red solutions.
Is rhodium a metal, nonmetal, or metalloid?
Rhodium is classified as a transition metal.
What state is rhodium at room temperature?
At about 25 °C, rhodium is a solid. It melts at 1963.8 °C.
What is rhodium used for?
Key uses include: catalytic converters (nox reduction); jewellery plating; aircraft spark-plug alloys.
Related elements
Keep working with this element
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