From New World Encyclopedia
71 ytterbiumlutetiumhafnium


periodic table
Name, Symbol, Number lutetium, Lu, 71
Chemical series lanthanides
Group, Period, Block n/a, 6, d
Appearance silvery white
Atomic mass 174.967(1) g/mol
Electron configuration Xe 6s2 4f14 5d1
Electrons per shell 2, 8, 18, 32, 9, 2
Physical properties
Phase solid
Density (near r.t.) 9.841 g/cm³
Liquid density at m.p. 9.3 g/cm³
Melting point 1925 K
(1652 °C, 3006 °F)
Boiling point 3675 K
(3402 °C, 6156 °F)
Heat of fusion ca. 22 kJ/mol
Heat of vaporization 414 kJ/mol
Heat capacity (25 °C) 26.86 J/(mol·K)
Vapor pressure
P/Pa 1 10 100 1 k 10 k 100 k
at T/K 1906 2103 2346 (2653) (3072) (3663)
Atomic properties
Crystal structure hexagonal
Oxidation states 3
(weakly basic oxide)
Electronegativity 1.27 (Pauling scale)
Ionization energies
1st: 523.5 kJ/mol
2nd: 1340 kJ/mol
3rd: 2022.3 kJ/mol
Atomic radius 175 pm
Atomic radius (calc.) 217 pm
Covalent radius 160 pm
Magnetic ordering no data
Electrical resistivity (r.t.) (poly) 582 nΩ·m
Thermal conductivity (300 K) 16.4 W/(m·K)
Thermal expansion (r.t.) (poly) 9.9 µm/(m·K)
Speed of sound (thin rod) (r.t.) 68.6 m/s
Shear modulus 27.2 GPa
Bulk modulus 47.6 GPa
Poisson ratio 0.261
Vickers hardness 1160 MPa
Brinell hardness 893 MPa
CAS registry number 7439-94-3
Notable isotopes
Main article: Isotopes of lutetium
iso NA half-life DM DE (MeV) DP
173Lu syn 1.37 y ε 0.671 173Yb
174Lu syn 3.31 y ε 1.374 174Yb
175Lu 97.41% Lu is stable with 104 neutrons
176Lu 2.59% 3.78×1010y β- 1.193 176Hf

Lutetium (chemical symbol Lu, atomic number 71) is a silvery white, metallic element that usually occurs in association with yttrium. It is the heaviest and hardest of the rare earth elements.[1] It is sometimes used in metal alloys and as a catalyst in various processes.


Found with almost all other rare-earth metals but never by itself, lutetium is very difficult to separate from other elements. Consequently, it is also one of the most expensive metals, costing about six times as much per gram as gold.

The principal commercially viable ore of lutetium is the rare earth phosphate mineral monazite, which contains 0.003 percent of the element. Pure lutetium metal has only relatively recently been isolated and is very difficult to prepare (thus it is one of the most rare and expensive of the rare earth metals). It is separated from other rare earth elements by ion exchange and then obtained in the elemental form by reduction of anhydrous LuCl3 or LuF3 by either an alkali metal or alkaline earth metal.


Lutetium (Latin Lutetia meaning Paris) was independently discovered in 1907 by French scientist Georges Urbain and Austrian mineralogist Baron Carl Auer von Welsbach. Both men found lutetium as an impurity in the mineral ytterbia which was thought by Swiss chemist Jean Charles Galissard de Marignac (and most others) to consist entirely of the element ytterbium.

The separation of lutetium from Marignac's ytterbium was first described by Urbain and the naming honor therefore went to him. He chose the names neoytterbium (new ytterbium) and lutecium for the new element but neoytterbium was eventually reverted back to ytterbium and in 1949 the spelling of element 71 was changed to lutetium.

Welsbach proposed the names cassiopium for element 71 (after the constellation Cassiopeia) and albebaranium for the new name of ytterbium but these naming proposals were rejected (although many German scientists in the 1950s called the element 71 cassiopium).

Notable characteristics

A strict correlation between periodic table blocks and chemical series for neutral atoms would describe lutetium as a transition metal because it is in the d-block, but it is classified as a lanthanide according to IUPAC.[2]

Lutetium is corrosion-resistant trivalent metal that is relatively stable in air.


Naturally occurring lutetium is composed of one stable isotope Lu-175 (97.41 percent natural abundance). 33 radioisotopes have been characterized, with the most stable being Lu-176 with a half-life of 3.78 × 1010 years (2.59 percent natural abundance), Lu-174 with a half-life of 3.31 years, and Lu-173 with a half-life of 1.37 years. All of the remaining radioactive isotopes have half-lifes that are less than nine days, and the majority of these have half lifes that are less than a half an hour. This element also has 18 meta states, with the most stable being Lu-177m (t½ 160.4 days), Lu-174m (t½ 142 days) and Lu-178m (t½ 23.1 minutes).

The isotopes of lutetium range in atomic weight from 149.973 (Lu-150) to 183.961 (Lu-184). The primary decay mode before the most abundant stable isotope, Lu-175, is electron capture (with some alpha and positron emission), and the primary mode after is beta emission. The primary decay products before Lu-175 are element 70 (ytterbium) isotopes and the primary products after are element 72 (hafnium) isotopes.


  • Fluoride:
    • lutetium(III) fluoride (LuF3)
  • Chloride:
    • lutetium(III) chloride (LuCl3)
  • Bromide:
    • lutetium(III) bromide (LuBr3)
  • Iodide:
    • lutetium(III) iodide (LuI3)
  • Oxide:
    • lutetium(III) oxide (Lu2O3)
  • Sulfide:
    • lutetium(III) sulfide (Lu2S3)
  • Nitride:
    • lutetium(III) nitride (LuN)

Intermetallic compounds:

  • Lutetium aluminum garnet (Al5Lu3O12)


As lutetium is very expensive to obtain in useful quantities, it has few commercial uses. Stable lutetium, however, can be used as a catalyst in petroleum cracking in refineries. It can also be used to catalyze reactions such as alkylation, hydrogenation, and polymerization.

Lutetium aluminum garnet has been proposed for use as a lens material in high refractive index immersion lithography.

Cerium-doped lutetium oxyorthosilicate (LSO) is currently the preferred compound for detectors in positron emission tomography (PET.)[3]


Like other rare-earth metals lutetium is regarded as having a low toxicity rating but it and especially its compounds should be handled with care nonetheless. Metal dust of this element is a fire and explosion hazard. Lutetium plays no biological role in the human body but is thought to help stimulate metabolism.

See also


  1. The term "rare earth metals" (or "rare earth elements") is a trivial name applied to 16 chemical elements: scandium, yttrium, and 14 of the 15 lanthanides (excluding promethium), which occur naturally on Earth. Some definitions also include the actinides. The word "earth" is an obsolete term for oxide. The term "rare earth" is discouraged by the International Union of Pure and Applied Chemistry (IUPAC), as these elements are relatively abundant in the Earth's crust.
  2. IUPAC Provisional Recommendations for the Nomenclature of Inorganic Chemistry (2004) (online draft of an updated version of the "Red Book" IR 3-6) Retrieved October 6, 2007.
  3. Thompson, C.J. “Instrumentation.” In: Wahl, R.L. (ed.). Principles and Practice of Positron Emission Tomography. Philadelphia: Lippincott Williams and Wilkins, 2002.

ISBN links support NWE through referral fees

  • Chang, Raymond. Chemistry. 9th ed. New York: McGraw-Hill Science/Engineering/Math, 2006. ISBN 0073221031
  • Cotton, F. Albert, and Geoffrey Wilkinson. Advanced Inorganic Chemistry. 4th ed. New York: Wiley, 1980. ISBN 0-471-02775-8
  • Greenwood, N.N. and A. Earnshaw. Chemistry of the Elements. 2nd ed. Oxford, U.K.; Burlington, MA: Butterworth-Heinemann, Elsevier Science, 1998. ISBN 0750633654 Online version Retrieved October 6, 2007.
  • Jones, Adrian P., Frances Wall, and C. Terry Williams, eds. Rare Earth Minerals: Chemistry, Origin and Ore Deposits. The Mineralogical Society Series. London, UK: Chapman and Hall, 1996. ISBN 0412610302
  • Stwertka, Albert. Guide to the Elements. Rev. ed. Oxford, UK: Oxford University Press, 1998. ISBN 0-19-508083-1
  • "Lutetium" Los Alamos National Laboratory, Chemistry Division. Retrieved Retrieved October 6, 2007.

External links

All links retrieved November 4, 2022.


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