Lutetium (Lu)
Lanthanide
Lutetium closes the lanthanide series as the hardest and densest rare earth. Its main starring role is medical: Lu-177 delivers targeted radiation to certain tumours, and lutetium crystals detect gamma rays in PET scanners.
Position on the periodic table
Atomic properties
| Atomic number | 71 |
|---|---|
| Atomic mass | 174.967 amu |
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d1 |
| Noble gas shorthand | [Xe] 4f14 5d1 6s2 |
| Electrons per shell | 2, 8, 18, 32, 9, 2 |
| Valence electrons (outer shell) | 2 |
| Common oxidation states | +3 |
| Electronegativity (Pauling) | 1.27 |
| Covalent radius (approx.) | 187 pm |
| First ionization energy | 523.5 kJ/mol |
| Electron affinity | 33.4 kJ/mol |
Physical properties
| State at 25 °C | Solid |
|---|---|
| Density | 9.841 g/cm³ |
| Melting point | 1651.8 °C (1925 K) |
| Boiling point | 3401.8 °C (3675 K) |
| Appearance | silvery white |
| Radioactive | No |
| Origin | Occurs naturally |
Electron configuration of lutetium
Lutetium's ground-state electron configuration is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d1, usually shortened to [Xe] 4f14 5d1 6s2. Its electrons occupy 6 shells (2, 8, 18, 32, 9, 2), placing it in period 6 of the d-block. Explore it interactively in the electron configuration calculator.
Uses of lutetium
- Targeted cancer therapy (Lu-177)
- PET scanner detector crystals
- Petroleum cracking catalysts
Biological role: None known.
Occurrence: The scarcest and most expensive stable rare earth.
Common compounds of lutetium
Lu2O3
Lutetium(III) oxide
History and discovery
Discovered: 1907 — Georges Urbain. Name origin: From Lutetia, the Roman name for Paris.
Georges Urbain separated lutetium from ytterbium in 1907, ending a priority dispute with Carl Auer von Welsbach.
Safety notes
Low chemical toxicity; medical isotopes are radioactive and clinically controlled.
Educational context only — always follow your school's laboratory rules and never handle chemicals without proper supervision. See our disclaimer.
Practice questions
Quick practice: Lutetium
1. What is the chemical symbol of Lutetium?
2. What is the atomic number of Lutetium?
3. Which category does Lutetium belong to?
4. What is the state of Lutetium at room temperature?
5. Which period of the periodic table is Lutetium in?
Lutetium FAQs
What is the atomic number of lutetium?
Lutetium's atomic number is 71 — every lutetium atom has 71 protons in its nucleus.
What is the symbol for lutetium?
Lu. From Lutetia, the Roman name for Paris.
Is lutetium a metal, nonmetal, or metalloid?
Lutetium is classified as a lanthanide.
What state is lutetium at room temperature?
At about 25 °C, lutetium is a solid. It melts at 1651.8 °C.
What is lutetium used for?
Key uses include: targeted cancer therapy (lu-177); pet scanner detector crystals; petroleum cracking catalysts.
Related elements
Keep working with this element
Spotted an error? Report a correction · Data sources