|Name , symbol , atomic number||Samarium, Sm, 62|
|Group , period , block||La , 6 , f|
|Mass fraction of the earth's envelope||6 ppm|
|Atomic mass||150.36 (2) u|
|Atomic radius (calculated)||185 (238) pm|
|Covalent radius||198 pm|
|Electron configuration||[ Xe ] 4 f 6 6 s 2|
|1. Ionization energy||5.64371 (17) eV ≈ 544.54 kJ / mol|
|2. Ionization energy||11.078 (20) eV ≈ 1 068.9 kJ / mol|
|3. Ionization energy||23.55 (8) eV ≈ 2 270 kJ / mol|
|4. Ionization energy||41.64 (11) eV ≈ 4 020 kJ / mol|
|5. Ionization energy||62.7 (4) eV ≈ 6 050 kJ / mol|
|density||7.536 g / cm 3 (25 ° C )|
|magnetism||paramagnetic ( Χ m = 1.2 · 10 −3 )|
|Melting point||1345 K (1072 ° C)|
|boiling point||2173 K (1900 ° C)|
|Molar volume||19.98 10 −6 m 3 mol −1|
|Heat of evaporation||192 kJ / mol|
|Heat of fusion||8.6 kJ mol −1|
|Speed of sound||2130 m s −1 at 293.15 K.|
|Electric conductivity||1.06 · 10 6 A · V −1 · m −1|
|Thermal conductivity||13 W m −1 K −1|
|Oxidation states||2, 3|
|Electronegativity||1.17 ( Pauling scale )|
|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 .
Samarium (after the mineral samarskite , which was named by the German mineralogist Heinrich Rose after the Russian mining engineer Vasily Samarski-Bychowez ) is a chemical element with the element symbol Sm and the atomic number 62. In the periodic table , the silvery element belongs to the group of lanthanides and is therefore also one of the rare earth metals . Samarium is the first naturally occurring element named after a person.
There are several representations of the discovery of the samarium in the literature.
- In 1853, the Swiss Jean Charles Galissard de Marignac demonstrated samarium spectroscopically using a sharp absorption line in didymoxide . In 1879, the Frenchman Paul Émile Lecoq de Boisbaudran isolated the element from the mineral samarskite ((Y, Ce, U, Fe) 3 (Nb, Ta, Ti) 5 O 16 ). Mineral and element names are derived from the Russian mining inspector (mining officer) Colonel Samarski-Bychowez , who discovered the mineral.
- In 1878, the Swiss chemist Marc Delafontaine discovered samarium, which he called decipum, in didymium oxide. In 1879, independently of him, Paul Émile Lecoq de Boisbaudran discovered the samarium. In 1881 Delafontaine shows that his isolated element contains another element besides samarium.
- The spectroscopic discovery of 1853 by Marignac mentioned under 1 was made in 1878 by Paul Émile Lecoq de Boisbaudran.
Samarium is currently obtained almost exclusively in China.
Extraction and presentation
Starting with monazite or bastnasite, rare earth metals are separated using ion exchange , solvent extraction or electrochemical deposition. In a final process step, the high-purity samarium oxide is reduced to the metal with metallic lanthanum and sublimed off .
Samarium is reasonably stable in air, it forms a passivating, yellowish oxide layer . Samarium with a metallic sheen ignites above 150 ° C. It reacts with oxygen to form sesquioxide Sm 2 O 3 . It reacts violently with water to form hydrogen and samarium hydroxide. As with all lanthanoids, the most stable oxidation state is +3.
Samarium comes in three modifications. The transition points are 734 ° C and 922 ° C. Sm 3+ cations turn aqueous solutions yellow.
There are four stable and 19 unstable radioactive isotopes . The most common natural isotopes are 152 Sm (26.7%), 154 Sm (22.7%) and 147 Sm (15%).
- Along with other rare earth metals for carbon arc lamps for film projection systems.
- Doping calcium fluoride single crystals for maser and laser .
- Because of its large cross-section for thermal and epithermal neutrons , samarium is used as a neutron absorber in nuclear applications. Since Sm-149 is also formed as a fission product, it is an unavoidable neutron poison in nuclear reactors.
- Samarium-Cobalt magnets :
Permanent magnets made of SmCo 5 have a high resistance to demagnetization and a coercive field strength of up to 2200 kA / m. The improved alloy Sm 2 Co 17 is more complex to manufacture, but has higher magnetic properties and improved corrosion resistance.
They are used in stepper motors for quartz clocks , drive motors in small tape recorders (Walkman, dictation machines), headphones, sensors , couplings in agitators and hard disk drives . As weight-saving magnetic materials, they are also used in the aerospace industry.
- Samarium oxide is optical glass for absorption of infrared added light.
- Samarium compounds are used to sensitize (luminous) phosphorus to irradiation with infrared light.
- As a catalyst ; Samarium oxide catalyzes the hydrogenation and dehydrogenation of ethanol (alcohol).
- Compounds with samarium in the less favorable oxidation state +2 (especially samarium (II) iodide and samarium (II) bromide) are used in organic synthesis (reducing agents and one-electron transfer reagent, e.g. samarium-mediated pinacol couplings) .
- In connection with the radiopharmaceutical ethylene diamine tetra (methylene phosphonic acid) in nuclear medicine for the palliative therapy of bone and skeletal metastases .
- In medicine, the isotope 153 samarium is used in conjunction with a bisphosphonate (Lexidronam) to treat bone pain in cancer ( radionuclide therapy for bone metastases ).
- Samarium (III) oxide Sm 2 O 3
- Samarium (III) fluoride SmF 3
- Samarium (III) chloride SmCl 3
- Samarium (II) bromide SmBr 2
- Samarium (III) bromide SmBr 3
- Samarium (II) iodide SmI 2
- Samarium (III) iodide SmI 3
- Samarium (III) sulfate Sm 2 (SO 4 ) 3
- Samarium-cobalt alloy, for example SmCo 5 and Sm 2 Co 17
- Samarium-153-EDTMP Samarium Ethylenediamine tetramethylene phosphonate
- 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 (Samarium) , unless otherwise stated .
- CIAAW, Standard Atomic Weights Revised 2013 .
- entry on samarium 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 samarium 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 .
- Norikazu Kinoshita et al: A Shorter 146 Sm Half-Life Measured and Implications for 146 Sm- 142 Nd Chronology in the Solar System. In: Science. Vol 335, Issue 6076, March 30, 2012, pp. 1614-1617. (PDF; 4.3 MB) Literature values so far: 103 ± 5 · 10 6 a.
- Samarium powder data sheet (PDF) from Merck , accessed April 26, 2017.
- Chemistry in Its Element - Samarium , Royal Society of Chemistry .
- Occurrence and production of mineral raw materials - a country comparison. (PDF) Federal Institute for Geosciences and Natural Resources, accessed on October 22, 2015 .
- Rare earths: dispute over China's market power enters a new round. In: heise.de. Retrieved October 22, 2015 .