|Name , symbol , atomic number||Terbium, Tb, 65|
|Group , period , block||La , 6 , f|
|Mass fraction of the earth's envelope||0.85 ppm|
|Atomic mass||158.92535 (2) and|
|Atomic radius (calculated)||175 (225) pm|
|Covalent radius||194 pm|
|Electron configuration||[ Xe ] 4 f 9 6 s 2|
|1. Ionization energy||5.8638 (6) eV ≈ 565.77 kJ / mol|
|2. Ionization energy||11.513 (20) eV ≈ 1 110.8 kJ / mol|
|3. Ionization energy||21st.82 (3) eV ≈ 2 110 kJ / mol|
|4. Ionization energy||39.33 (4) eV ≈ 3 790 kJ / mol|
|5. Ionization energy||66.5 (3) eV ≈ 6 420 kJ / mol|
|density||8.253 g / cm 3 (25 ° C )|
|magnetism||paramagnetic ( Χ m = 0.11)|
|Melting point||1629 K (1356 ° C)|
|boiling point||3396 K (3123 ° C)|
|Molar volume||19.30 · 10 −6 m 3 · mol −1|
|Heat of evaporation||391 kJ / mol|
|Heat of fusion||10.8 kJ mol −1|
|Speed of sound||2620 m s −1 at 293.15 K.|
|Electric conductivity||0.870 · 10 6 A · V −1 · m −1|
|Thermal conductivity||11 W m −1 K −1|
|Oxidation states||4, 3|
|For other isotopes see list of isotopes|
As far as possible and customary, SI units are used.
Unless otherwise noted, the data given apply to standard conditions .
Terbium is a chemical element with the element symbol Tb and the atomic number 65. In the periodic table it is in the group of lanthanoids and is therefore one of the rare earth metals . Terbium is named after its first location, the Ytterby mine near Stockholm , as are yttrium , ytterbium and erbium .
The discovery of the element terbium is very confused and has not yet been clarified. Generally one sees Carl Gustav Mosander as explorers, the early 1840s by Johan Gadolin discovered yttria examined. The supposedly pure terbium compound was a mixture of several lanthanoids (Bunsen).
Pure terbium was only produced after 1945 with the advent of ion exchange technology.
Mosander derived the element designation from the name of the Swedish mine Ytterby .
Terbium occurs naturally only in compounds. Well-known minerals containing terbium are:
- Monazite (Ce, La, Th, Nd, Y) PO 4 with a Tb content of max. 0.03%, the main ore for Tb
- Gadolinite (deposits at Ytterby are exhausted)
- Euxenite (Y, Ca, Er, La, Ce, U, Th) (Nb, Ta, Ti) 2 O 6 with a Tb content of max. 1 %
Extraction and presentation
After a complex separation of the other terbium companions, the oxide is converted with hydrogen fluoride to terbium fluoride . It is then reduced to terbium with calcium to form calcium fluoride . The removal of remaining calcium residues and impurities takes place in an additional remelting process in a vacuum .
The silver-gray metal of the rare earths is ductile and malleable . At temperatures above 1315 ° C, α-terbium ( hcp crystal lattice ) is converted into β-terbium. Terbium is relatively stable in air , it is covered with an oxide layer. It burns in the flame to form brown terbium (III, IV) oxide (Tb 4 O 7 ). With water it reacts with evolution of hydrogen to hydroxide .
Terbium is for doping of calcium fluoride , calcium tungstate and strontium molybdate for use in semiconductors used (solid-state devices). Together with zirconium (IV) oxide , it is used to stabilize the structure in high-temperature fuel cells . The oxide is added to the green phosphor in picture tubes and fluorescent lamps . Sodium terbium borate is used as a laser material to generate coherent light with a wavelength of 546 nm (green).
Terbium- iron - cobalt or terbium- gadolinium- iron-cobalt alloys are used as coatings on rewritable magneto-optical (MO) discs. Alloys containing terbium- dysprosium show strong magnetostriction (change in length due to a magnetic field or magnetic impulses when length changes). Such alloys are used in materials testing technology.
Terbium and terbium compounds are considered to be of low toxicity. The element has no biological significance for the human organism. Terbium metal dusts, like almost all metal dusts, are flammable and explosive.
In compounds, terbium occurs in the oxidation states +2, +3, +4.
- Terbium (III) sulfate Tb 2 (SO 4 ) 3 · 8 H 2 O: colorless crystals which fluoresce yellow-green when excited with short-wave UV radiation .
- Harry H. Binder: Lexicon of the chemical elements. S. Hirzel Verlag, Stuttgart 1999, ISBN 3-7776-0736-3 .
- The values for the properties (info box) are taken from www.webelements.com (Terbium) , unless otherwise stated .
- CIAAW, Standard Atomic Weights Revised 2013 .
- Entry on terbium in Kramida, A., Ralchenko, Yu., Reader, J. and NIST ASD Team (2019): NIST Atomic Spectra Database (ver. 5.7.1) . Ed .: NIST , Gaithersburg, MD. doi : 10.18434 / T4W30F ( https://physics.nist.gov/asd ). Retrieved June 13, 2020.
- Entry on terbium at WebElements, https://www.webelements.com , accessed on June 13, 2020.
- NN Greenwood, A. Earnshaw: Chemistry of the elements. 1st edition. VCH, Weinheim 1988, ISBN 3-527-26169-9 , p. 1579.
- Robert C. Weast (Ed.): CRC Handbook of Chemistry and Physics . CRC (Chemical Rubber Publishing Company), Boca Raton 1990, ISBN 0-8493-0470-9 , pp. E-129 to E-145. Values there are based on g / mol and given in cgs units. The value specified here is the SI value calculated from it, without a unit of measure.
- Yiming Zhang, Julian RG Evans, Shoufeng Yang: Corrected Values for Boiling Points and Enthalpies of Vaporization of Elements in Handbooks. In: Journal of Chemical & Engineering Data . 56, 2011, pp. 328-337, doi: 10.1021 / je1011086 .
- Terbium data sheet at Sigma-Aldrich , accessed on April 26, 2017 ( PDF ).
- Rompp's chemical dictionary, May 1974, Volume 3, p. 847.