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Lutetium (Lu)
Lutetium (symbol Lu) is the chemical element with atomic number 71: a lanthanide (rare earth), solid at 0 °C, with an atomic mass of 174.97 u. Discovered in 1907 (Georges Urbain).
Lutetium closes the lanthanide series: it is the densest, hardest and most heat-resistant of them all. Its radioactive isotope lutetium-177, attached to molecules that seek out tumors, has become a flagship treatment for some prostate cancers and neuroendocrine tumors. Its name comes from Lutetia, the ancient name of Paris.
Key facts
- Atomic number
- 71
- Symbol
- Lu
- French name
- Lutécium
- Atomic mass
- 174.97 u
- Molar mass
- 174.97 g/mol
- Family
- Lanthanides
- Position
- period 6, d-block
- State at 0 °C
- Solid
- Melting point
- 1,651.9 °C
- Boiling point
- 3,401.9 °C
- Density
- 9.84 g/cm³
- Electronegativity (Pauling)
- 1.27
- First ionization energy
- 524 kJ/mol
- Atomic radius
- 175 pm
- Electron configuration
- [Xe] 4f¹⁴ 5d¹ 6s²
- Abundance in Earth's crust
- 0.8 ppm (61st most abundant element)
- Indicative price
- 640 $/kg (order of magnitude)
- Radioactive
- no
- Discovery
- 1907, Georges Urbain
Origin of the name
From Lutetia, the Latin name for Paris.
What does lutetium look like?
A dense (9.8 g/cm³) silvery-white metal, fairly resistant to corrosion. It melts at around 1,660 °C.
Where is lutetium found?
About 0.8 ppm of Earth's crust. It comes mainly from xenotime and ionic clays, where it makes up only a small fraction of the rare earths.
Natural sources
- Xenotime
- Monazite
- Ion-adsorption clays
How is lutetium produced?
Isolated by ion exchange, then reduced with calcium. It is one of the most expensive rare earths. Medical lutetium-177 is made in nuclear reactors from lutetium-176 or ytterbium-176.
Top producers
- China
- Myanmar
What is lutetium used for?
- Lutetium-177 in targeted cancer radiotherapy.
- Scintillator crystals (LSO, LYSO) in PET scanners.
- Lutetium-hafnium dating of ancient rocks.
- Petrochemical catalysts.
In everyday life
- A PET scan at the hospital
- Targeted internal radiotherapy
Role in living things
No known biological role.
Hazards of lutetium
Low chemical toxicity. Lutetium-177 is radioactive: treated patients follow temporary precautions to limit exposure to those around them.
Cosmic origin
- Neutron stars: Created when two neutron stars collide — the “forge” of gold.
- Dying stars: Made slowly in red giants (stars like the Sun at the end of their lives).
History of lutetium
In 1907 three chemists discovered it almost simultaneously: the Frenchman Georges Urbain, the Austrian Carl Auer von Welsbach and the American Charles James. Urbain published first and named it after Lutetia; Auer von Welsbach preferred “cassiopeium,” a name used in Germany until the 1950s.
Did you know?
- Natural lutetium-176 is radioactive, with a half-life of about 37 billion years.
- The drug Pluvicto, based on lutetium-177, was approved in 2022 for metastatic prostate cancer.
- It is the only element named after Paris.
Isotopes of lutetium
Natural lutetium contains one stable isotope, lutetium-175, and 2.6% radioactive lutetium-176. Lutetium-177, made in reactors, has become a star of nuclear medicine.
- lutetium-175: 97.401% of natural lutetium, stable
- lutetium-176: 2.599% of natural lutetium, radioactive, half-life 3.7 × 10¹⁰ years. Turns into hafnium-176: lutetium–hafnium dating is used on ancient rocks.
- lutetium-177: radioactive, half-life 6.65 days. Targeted internal radiotherapy for some prostate cancers and neuroendocrine tumors.
Related elements
Same family (lanthanides): Lanthanum (La), Cerium (Ce), Praseodymium (Pr), Neodymium (Nd), Promethium (Pm), Samarium (Sm), Europium (Eu), Gadolinium (Gd), Terbium (Tb), Dysprosium (Dy), Holmium (Ho), Erbium (Er), Thulium (Tm), Ytterbium (Yb).