2007 Schools Wikipedia Selection. Related subjects: Chemical elements

71 ytterbiumlutetiumhafnium


Periodic Table - Extended Periodic Table
Name, Symbol, Number lutetium, Lu, 71
Chemical series Transition metals
Group, Period, Block 3, 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·cm−3
Liquid density at m.p. 9.3 g·cm−3
Melting point 1925  K
(1652 ° C, 3006 ° F)
Boiling point 3675 K
(3402 ° C, 6156 ° F)
Heat of fusion ca. 22 kJ·mol−1
Heat of vaporization 414 kJ·mol−1
Heat capacity (25 °C) 26.86 J·mol−1·K−1
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
( more)
1st: 523.5 kJ·mol−1
2nd: 1340 kJ·mol−1
3rd: 2022.3 kJ·mol−1
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−1·K−1
Thermal expansion ( r.t.) (poly) 9.9 µm/(m·K)
Young's modulus 68.6 GPa
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
Selected 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% 3.78×1010 y β- 1.193 176Hf

Lutetium ( IPA: /l(j)uːˈtiːʃiəm/) is a chemical element with the symbol Lu and atomic number 71. A metallic element of the transition metal group, lutetium usually occurs in association with yttrium and is sometimes used in metal alloys and as a catalyst in various processes. Though it is a transition metal according to factors like its place in the Periodic Table, its electron orbital configuration, and its physical properties, it is often grouped with the lanthanides.

Notable characteristics and applications

Lutetium is a silvery white corrosion-resistant trivalent metal that is relatively stable in air and is the heaviest and hardest of the rare earth elements.

This element is very expensive to obtain in useful quantities and therefore it has very few commercial uses. However, stable lutetium can be used as catalysts in petroleum cracking in refineries and can also be used in alkylation, hydrogenation, and polymerization applications.

Lutetium aluminium garnet (Al5Lu3O12) 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.)


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 honour 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 where rejected (although many German scientists in the 1950s called the element 71 cassiopium).


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: (Ce, La, etc.)PO4 which contains 0.003% 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.


Naturally occurring lutetium is composed of 1 stable isotope Lu-175 (97.41% 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% 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 9 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: LuF3, Chloride: LuCl3, Bromide: LuBr3, Iodide: LuI3, Oxide: Lu2O3, Sulfide: Lu2S3, Nitride: LuN

Intermetalic compounds:

  • Lutetium aluminium garnet


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.

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