Samarium

properties
General
Name , symbol , atomic number	Samarium, Sm, 62
Element category	Lanthanoids
Group , period , block	La , 6 , f
Appearance	silvery white
CAS number	7440-19-9
EC number	231-128-7
ECHA InfoCard	100.028.298
Mass fraction of the earth's envelope	6 ppm
Atomic
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
Physically
Physical state	firmly
Crystal structure	trigonal
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
Chemically
Oxidation states	2, 3
Electronegativity	1.17 ( Pauling scale )
Isotopes
For other isotopes see list of isotopes
NMR properties
safety instructions
GHS labeling of hazardous substances powder danger
H and P phrases	H: 260
	P: 402 + 404
	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.

history

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.

In 1903, the German chemist Wilhelm Muthmann produced metallic samarium using electrolysis .

Occurrence

Samarium in ampoule under argon gas

Samarium is currently obtained almost exclusively in China.

Elementary samarium does not appear dignified. However, some minerals such as monazite , bastnasite and samarskite contain the element. Monazite contains up to 1% samarium.

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 .

properties

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.

Isotopes

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%).

use

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 ).

links

Samarium (III) oxide Sm ₂ O 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

Web links

Commons : Samarium - collection of images, videos and audio files

Wiktionary: Samarium - explanations of meanings, word origins, synonyms, translations

Entry to samarium. In: Römpp Online . Georg Thieme Verlag, accessed on January 3, 2015.

Individual evidence

^ 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 .

↑ ^a ^b ^c ^d ^e 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.

↑ ^a ^b ^c ^d ^e 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.

↑ ^a ^b 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.

↑ ^a ^b Samarium powder data sheet (PDF) from Merck , accessed April 26, 2017.

^ ^A ^b 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 .

[Harry_H._Binder-1] Harry H. Binder: Lexicon of the chemical elements. S. Hirzel Verlag, Stuttgart 1999, ISBN 3-7776-0736-3 .

[2] The values for the properties (info box) are taken from www.webelements.com (Samarium) , unless otherwise stated .

[CIAAW-3] CIAAW, Standard Atomic Weights Revised 2013 .

[NIST-ASD-samarium-4] ↑ ^a ^b ^c ^d ^e 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.

[Webelements-samarium-5] Entry on samarium at WebElements, https://www.webelements.com , accessed on June 13, 2020.

[Greenwood-6] NN Greenwood, A. Earnshaw: Chemistry of the elements. 1st edition. VCH, Weinheim 1988, ISBN 3-527-26169-9 , p. 1579.

[7] 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.

[Zhang-8] 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 .

[9] 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.