Lutetium
Atomic Data
| Atomic Number | 71 |
| Symbol | Lu |
| Atomic Weight | 174.97 u |
| Density (STP) | 9.841 g/cm³ |
| Melting Point | 1651.85 °C (1925 K) |
| Boiling Point | 3401.85 °C (3675 K) |
| Electronegativity | 1.27 (Pauling) |
| Electron Config. | 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d1 6s2 |
| Oxidation States | +3 |
| Phase at STP | Solid |
| Category | Lanthanoid |
| Period / Group | 6 / None |
| CAS Number | 7439-94-3 |
Electron Configuration
[Xe] 4f14 5d1 6s2
| Shell | n | Subshell | Electrons | Cumulative |
|---|---|---|---|---|
| K | 1 | 1s | 2 | 2 |
| L | 2 | 2s | 2 | 4 |
| L | 2 | 2p | 6 | 10 |
| M | 3 | 3s | 2 | 12 |
| M | 3 | 3p | 6 | 18 |
| M | 3 | 3d | 10 | 28 |
| N | 4 | 4s | 2 | 30 |
| N | 4 | 4p | 6 | 36 |
| N | 4 | 4d | 10 | 46 |
| N | 4 | 4f | 14 | 60 |
| O | 5 | 5s | 2 | 62 |
| O | 5 | 5p | 6 | 68 |
| O | 5 | 5d | 1 | 69 |
| P | 6 | 6s | 2 | 71 |
| Total | 71 | 71 | ||
Isotopes of Lutetium
Lutetium has two naturally occurring stable isotopes. The most abundant is ¹⁷⁵Lu, comprising 97.401% of all naturally occurring Lutetium.
| Isotope | Symbol | Protons | Neutrons | Abundance | Stability |
|---|---|---|---|---|---|
| Lutetium-175 | ¹⁷⁵Lu | 71 | 104 | 97.401 | Stable |
| Lutetium-176 | ¹⁷⁶Lu | 71 | 105 | 2.599 | Stable |
Abundance & Occurrence
Lutetium is present in Earth's crust at approximately 0.8 ppm by mass and at approximately 0.01 ppm by mass throughout the universe.
Earth's Crust (ppm by mass)
Universe (ppm by mass)
Discovery & History
Read more about the discovery of the periodic table of elements →
Safety & Handling
- Dust inhalation: Lutetium metal dust and oxide are respiratory irritants; use ventilation and respiratory protection when machining or handling fine lutetium powders.
- Lutetium-177: medical radiation: Lu-177 (t½ = 6.7 days, beta/gamma) is used in targeted radionuclide therapy; medical staff administering Lu-177 therapies must follow radiation protection procedures including dosimetry, shielding, and patient waste management.
- Fire hazard: Lutetium metal powder is flammable; metal fires require Class D extinguishing agents.
- General toxicity: Lutetium has low acute systemic toxicity; the primary hazards are occupational dust inhalation during processing and radiation from its medical radioisotope.
Lutetium in the Real World
Real-World Uses
- PET scanner detector crystals: Lutetium oxyorthosilicate (LSO) and lutetium yttrium oxyorthosilicate (LYSO) are the preferred scintillator crystals in modern PET scanners due to their high density, fast decay time, and high light output, enabling faster whole-body scans at lower radiation dose.
- Targeted radionuclide therapy: Lutetium-177 (t½ = 6.65 d) attached to tumour-targeting peptides (DOTA-TATE for somatostatin receptors, PSMA-617 for prostate-specific membrane antigen) delivers localised beta radiation to neuroendocrine tumours and prostate cancer metastases.
- Petroleum cracking catalysts: Lutetium oxide is added to zeolite FCC catalysts in oil refineries to improve thermal and hydrothermal stability, maintaining catalyst activity during the high-temperature regeneration cycles of fluid catalytic cracking units.
- Alloy research: Lutetium, the densest and hardest lanthanide, is studied as an additive to improve the high-temperature stability and corrosion resistance of aluminium and iron-based alloys for aerospace applications.
Downloadable Resources
Free periodic table reference sheets for classrooms, study sessions, and laboratory use.
Frequently Asked Questions
What is lutetium used for?
Lutetium oxyorthosilicate (LSO) doped with cerium is used as a scintillator crystal in PET (positron emission tomography) scanners, where it detects the gamma rays produced when positrons from radioactive tracers annihilate with electrons in the patient's body. Lutetium-177, a radioactive isotope, is used in targeted radionuclide therapy for neuroendocrine tumours and prostate cancer. Lutetium also acts as a catalyst in petroleum refining.
Is lutetium used in cancer treatment?
Yes. Lutetium-177, produced in nuclear reactors, is used in targeted radionuclide therapy. When attached to tumour-seeking molecules (such as DOTATATE for neuroendocrine tumours or PSMA ligands for prostate cancer), Lu-177 delivers beta radiation directly to cancer cells. The drug Lutathera (177Lu-DOTATATE) and Pluvicto (177Lu-PSMA-617) are approved treatments representing a major advance in precision oncology.
How was lutetium discovered?
Lutetium was discovered independently in 1907 by French chemist Georges Urbain and Austrian mineralogist Carl Auer von Welsbach, both separating it from ytterbium compounds. There was a priority dispute, but Urbain published first. He named it lutetium after Lutetia, the Latin name for Paris. It was the last stable rare-earth element to be discovered.
Why is LSO crystal important in PET scanning?
In a PET scanner, a patient is injected with a positron-emitting radiotracer. When a positron annihilates with an electron in tissue, two 511 keV gamma rays fly off in opposite directions. Lutetium oxyorthosilicate (LSO) crystals detect these gamma rays rapidly: LSO has a very short scintillation decay time (about 40 ns) and high density (7.4 g/cm3), allowing the scanner to pinpoint the annihilation event accurately and quickly. This enables high-resolution, fast PET imaging essential for cancer diagnosis and staging.