Lutetium Facts – Atomic Number 71 or Lu

This is a photo of a 1-cm chunk of pure lutetium. Lutetium is a silvery-white corrosion-resistant metal. Jurii, Creative Commons License
This is a photo of a 1-cm chunk of pure lutetium. Lutetium is a silvery-white corrosion-resistant metal. Jurii, Creative Commons License

Lutetium is a dense, silvery-white rare earth metal. Here is a collection of interesting element facts for lutetium or cassiopeium:

  • Lutetium was the last natural rare earth element that was discovered. It was discovered in 1907 by three scientists, working independently from each other. Georges Urbain, Charles James, and Carl Auer von Welsbach all extracted lutetium from a sample of the mineral ytterbia. Urbain is often credited for the discovery of the element because his results were published first.
  • The element originally was named lutecium. In 1949, the name was officially changed to lutetium, in keeping with naming of other elements.
  • Lutetium is the hardest lanthanide element.
  • It’s also the most expensive lanthanide.
  • Atoms of lutetium are the smallest of any lanthanide element.
  • Lutetium metal is silvery-white, soft, malleable, and ductile.
  • Lutetium is never found naturally in pure form. Sources of lutetium include nearly all minerals which contain the similar element, yttrium. A commercial source of lutetium is monazite, which consists of about 0.003 percent lutetium.
  • Two naturally occurring isotopes of lutetium have been identified. Lutetium-175 is a stable isotope. The other natural isotope, lutetium-176, has a half-life of nearly 38 trillion years. 32 synthetic radioisotopes have been synthesized.
  • Pure lutetium is obtained by reduction of anhydrous LuCl3 or LuF3 using an alkali metal or alkaline earth metal. Only about 10 tons of lutetium are produced globally each year.
  • The primary use of lutetium is in the petroleum industry as a catalyst.

Lutetium Chemical and Physical Properties

Various forms of lutetium. (Alchemist-hp)
Various forms of lutetium. (Alchemist-hp)

Element Name: Lutetium (German Cassiopeium)

Atomic Number: 71

Symbol: Lu

Atomic Weight: 174.967

Discovery: Georges Urbain 1907 (France)

Electron Configuration: [Xe] 4f14 5d1 6s2

Element Classification: Rare Earth (Lanthanide Series)

Word Origin: Named for the ancient name of Paris, Lutecia.

Density (g/cc): 9.8404

Melting Point (K): 1936

Boiling Point (K): 3668

Lutetium Electron Configuration
Lutetium Electron Configuration

Appearance: silvery-white, hard, dense metal

Atomic Radius (pm): 175

Atomic Volume (cc/mol): 17.8

Covalent Radius (pm): 156

Ionic Radius: 85 (+3e)

Specific Heat (@20°C J/g mol): 0.155

Evaporation Heat (kJ/mol): 414

Pauling Negativity Number: 1.27

First Ionizing Energy (kJ/mol): 513

Oxidation States: 3

Lattice Structure: Hexagonal

Lattice Constant (Å): 3.510

Lattice C/A Ratio: 1.585


  • Los Alamos National Laboratory (2001).
  • Crescent Chemical Company (2001).
  • Lange’s Handbook of Chemistry (1952).
  • CRC Handbook of Chemistry & Physics (18th ed.).