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Element Fact
Cesium is used in atomic clock. As in 1999, the best clock is accurate to a second in 20 million years.

Lutetium, Lu

lutetium sample

Atomic number: 71
Atomic mass: 174.967(1)
Natural abundance: 0.8 ppm
175Lu (174.940768) - 97.41%
176Lu (175.942682) - 2.59%

History and Production

From Lutetia, ancient name for Paris. Discovered in 1907 by G. Urbain from a concentrate of Marignac's ytterbium mixture (1878). The metal was independently discovered by C.A. von Welsbach who named the element as 'cassiopeium', as is still sometimes referred to by the Germans. Commercially it is obtained from monazite which contains up to 0.003% of the metal. Ion-exchange tenchnique is required to separate its salts from other rare earths. The metal itself is obtained by halides (such as chloride and fluoride) reduction with calcium metal. Commercial and industrial uses of the metal are still not common. However, the isotope 176Lu, with a half-life of about 3 x 1010 years, is used to determined the age of meteorite relative to Earth.

Physical Data

The metal is silvery white and relatively stable in air. It consists of 0.8 ppm of the earth's crust and often associated with other rare earth in minerals such as monazite.

Interatomic distance: 343.6 pm
Melting point: 1663C
Boiling point: 3402C
Thermal conductivity/Wm-1K-1: 16.4 (27C)
Density/kgm-3: 9841 (25C)

Standard Thermodynamic Data (atomic gas)

Enthalpy of formation: 152.3 kJ/mol
Gibbs free energy of formation: 118.48 kJ/mol
Entropy: 173.1 J/mol K
Heat capacity: 20.8 J/mol K

Electronic data

Electronic configuration: [Xe] 4f14 5d1 6s2
Term symbol: 2D3/2
Electron affinity: -   Electronegativity (Pauline): 1.0
Ionization energy (first, second, third): 523.520, 1341.15, 2022.28 kJ/mol

Chemical properties

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