The last of the lanthanides — and the heaviest of them all. Lutetium wraps up the series of 15 rare-earth elements with a record density of 9.84 g/cm³. This silvery-white metal is so scarce that Earth's crust holds only 0.5 ppm of it. That's less than silver.
The element is named after Lutetia, the ancient Roman name for Paris. Three scientists discovered it independently in 1907. Today, lutetium treats cancer, helps geologists date the oldest rocks on the planet, and boosts catalysts in oil refineries.
In pure form, lutetium is a shiny, silvery metal that resists corrosion in air. It melts at 1,663 °C and boils at 3,402 °C. It has just one stable isotope — Lu-175 (97.4% in nature). The second isotope, Lu-176, is radioactive with a half-life of 37.6 billion years — three times the age of the universe.
Extracting lutetium is extremely difficult: it must be separated from other lanthanides through repeated solvent extraction. That's why a kilogram of pure lutetium costs thousands of dollars.
Metallic lutetium has low toxicity and is safe for brief skin contact. However, fine lutetium dust is combustible — it can ignite on contact with a spark or flame. Radioactive isotopes (Lu-177, Lu-176) require protection against ionizing radiation. Working with lutetium compounds calls for protective gloves, goggles, and good ventilation. Ingesting soluble compounds may irritate the gastrointestinal tract.
Lutetium is the heaviest and densest of all 15 lanthanides. Its atomic radius is the smallest in the series due to the 'lanthanide contraction' — a unique effect where 4f electrons poorly shield the nucleus.
The element is named after Lutetia, the ancient Roman name for Paris. French chemist Georges Urbain proposed the name in 1907, winning a naming dispute with an Austrian scientist.
Isotope Lu-176 has a half-life of 37.6 billion years — three times longer than the age of the universe. Geologists use it to date the oldest rocks on Earth and meteorites.
Radioactive Lu-177 has become a breakthrough in oncology. It delivers beta radiation directly to cancer cells, destroying tumors from within. The FDA approved the Lu-177-based drug Pluvicto in 2022.
Lu₂SiO₅ (LSO) crystals are among the best scintillators in the world. They convert gamma rays into flashes of light in PET scanners, helping doctors spot tumors as small as 4 mm.
Lutetium is added to petroleum cracking catalysts. It improves their efficiency and stability, helping convert heavy oil fractions into gasoline and diesel.
| Isotope | Mass (u) | Abundance | Half-life | Decay |
|---|---|---|---|---|
175Lu | 174.940772 | 97.41% | stable | — |
176Lu☢ | 175.942686 | 2.59% | 3.76×10¹⁰ years | β− |
Separation from ytterbia