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Element Fact
Americium is one of the few radioactive elements that find its use in homes as a smoke detector.

Terbium, Tb

terbium sample

Atomic number: 65
Atomic mass: 158.92534(2)
Natural abundance: 1.2 ppm
159Tb (158.92534) - 100%

History and Production

Derived from a Swedish village Ytterby. It was discovered by C.G. Mosander in 1843 from the mineral yttria. It can be recovered as a byproduct from monazite, a mixture of rare earth phosphates that contain about 0.03% of terbium. It is also obtained from euxenite, an oxide complex. Ion-exchange techniques are used to separate terbium salts from other rare earths and the metal is subsequently obtained by reduction of the fluoride with calcium metal. The metal is used to make laser (sodium terbium borate) and as a dopant in calcium fluoride, strontium molybdate and calcium tungstate for solid-state devices.

Physical Data

It is a silvery grey metal that reacts slowly with air and water. It is malleable and ductile and can be cut with a knife. Its natural abundance is 1.2 ppm and is usually associated with other rare earth metals in monazite, xenotime and euxinite.

Interatomic distance: 352.6 pm
Melting point: 1356C
Boiling point: 3230C
Thermal conductivity/Wm-1K-1: 11.1 (27C)
Density/kgm-3: 8229 (20C)

Standard Thermodynamic Data (atomic gas)

Enthalpy of formation: 388.7 kJ/mol
Gibbs free energy of formation: 349.7 kJ/mol
Entropy: 203.6 J/mol K
Heat capacity: 24.6 J/mol K

Electronic data

Electronic configuration: [Xe] 4f9 6s2
Term symbol: 6H15/2
Electron affinity: -   Electronegativity (Pauline): -
Ionization energy (first, second, third): 565.771, 1111.51, 2114.00 kJ/mol

Chemical properties

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