Samarium

Samarium, ₆₂Sm
Samarium
Pronunciation	/səˈmɛəriəm/ (sə-MAIR-ee-əm)
Appearance	silvery white
Standard atomic weight Ar°(Sm)
	150.36±0.02; 150.36±0.02 (abridged);
Samarium in the periodic table
	promethium ← samarium → europium
Atomic number (Z)	62
Group	f-block groups (no number)
Period	period 6
Block	f-block
Electron configuration	[Xe] 4f6 6s2
Electrons per shell	2, 8, 18, 24, 8, 2
Physical properties
Phase at STP	solid
Melting point	1345 K (1072 °C, 1962 °F)
Boiling point	2173 K (1900 °C, 3452 °F)
Density (at 20° C)	7.518 g/cm3
when liquid (at m.p.)	7.16 g/cm3
Heat of fusion	8.62 kJ/mol
Heat of vaporization	192 kJ/mol
Molar heat capacity	29.54 J/(mol·K)
Atomic properties
Oxidation states	common: +3; 0, +1, +2
Electronegativity	Pauling scale: 1.17
Ionization energies	1st: 544.5 kJ/mol ; 2nd: 1070 kJ/mol ; 3rd: 2260 kJ/mol ; ;
Atomic radius	empirical: 180 pm
Covalent radius	198±8 pm
	Spectral lines of samarium
Other properties
Natural occurrence	primordial
Crystal structure	rhombohedral (hR3)
Lattice constants	ar = 0.89834 nm; α = 23.307°; ah = 0.36291 nm; ch = 2.6207 nm (at 20 °C)
Thermal expansion	poly: 12.7 (at r.t.) µm/(m⋅K)
Thermal conductivity	13.3 W/(m⋅K)
Electrical resistivity	α, poly: 0.940 (at r.t.) µΩ⋅m
Magnetic ordering	paramagnetic
Molar magnetic susceptibility	+1860.0×10−6 cm3/mol (291 K)
Young's modulus	49.7 GPa
Shear modulus	19.5 GPa
Bulk modulus	37.8 GPa
Speed of sound thin rod	2130 m/s (at 20 °C)
Poisson ratio	0.274
Vickers hardness	410–440 MPa
Brinell hardness	440–600 MPa
CAS Number	7440-19-9
History
Naming	after the mineral samarskite (itself named after Vassili Samarsky-Bykhovets)
Discovery and first isolation	Lecoq de Boisbaudran (1879)
Isotopes of samarium v; e;
	Category: Samarium; view; talk; edit; \| references

Samarium is a chemical element; it has symbol Sm and atomic number 62. It is a moderately hard silvery metal that slowly oxidizes in air. Being a typical member of the lanthanide series, samarium usually has the oxidation state +3. Compounds of samarium(II) are also known, most notably the monoxide SmO, monochalcogenides SmS, SmSe and SmTe, as well as samarium(II) iodide.

Discovered in 1879 by French chemist Paul-Émile Lecoq de Boisbaudran, samarium was named after the mineral samarskite from which it was isolated. The mineral itself was named after a Russian mine official, Colonel Vassili Samarsky-Bykhovets, who thus became the first person to have a chemical element named after him, though the name was indirect.

Samarium occurs in concentration up to 2.8% in several minerals including cerite, gadolinite, samarskite, monazite and bastnäsite, the last two being the most common commercial sources of the element. These minerals are mostly found in China, the United States, Brazil, India, Sri Lanka and Australia; China is by far the world leader in samarium mining and production.

The main commercial use of samarium is in samarium–cobalt magnets, which have permanent magnetization second only to neodymium magnets; however, samarium compounds can withstand significantly higher temperatures, above 700 °C (1,292 °F), without losing their permanent magnetic properties. The radioisotope samarium-153 is the active component of the drug samarium (¹⁵³Sm) lexidronam (Quadramet), which kills cancer cells in lung cancer, prostate cancer, breast cancer and osteosarcoma. Another isotope, samarium-149, is a strong neutron absorber and so is added to control rods of nuclear reactors. It also forms as a decay product during the reactor operation and is one of the important factors considered in the reactor design and operation. Other uses of samarium include catalysis of chemical reactions, radioactive dating and X-ray lasers. Samarium(II) iodide, in particular, is a common reducing agent in chemical synthesis.

Samarium has no biological role; some samarium salts are slightly toxic.^[11]

^ "Standard Atomic Weights: Samarium". CIAAW. 2005.
^ Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; Böhlke, John K.; Chesson, Lesley A.; Coplen, Tyler B.; Ding, Tiping; Dunn, Philip J. H.; Gröning, Manfred; Holden, Norman E.; Meijer, Harro A. J. (2022-05-04). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.
^ ^a ^b Arblaster, John W. (2018). Selected Values of the Crystallographic Properties of Elements. Materials Park, Ohio: ASM International. ISBN 978-1-62708-155-9.
^ Yttrium and all lanthanides except Ce and Pm have been observed in the oxidation state 0 in bis(1,3,5-tri-t-butylbenzene) complexes, see Cloke, F. Geoffrey N. (1993). "Zero Oxidation State Compounds of Scandium, Yttrium, and the Lanthanides". Chem. Soc. Rev. 22: 17–24. doi:10.1039/CS9932200017. and Arnold, Polly L.; Petrukhina, Marina A.; Bochenkov, Vladimir E.; Shabatina, Tatyana I.; Zagorskii, Vyacheslav V.; Cloke (2003-12-15). "Arene complexation of Sm, Eu, Tm and Yb atoms: a variable temperature spectroscopic investigation". Journal of Organometallic Chemistry. 688 (1–2): 49–55. doi:10.1016/j.jorganchem.2003.08.028.
^ SmB₆^- cluster anion has been reported and contains Sm in rare oxidation state of +1; see Paul, J. Robinson; Xinxing, Zhang; Tyrel, McQueen; Kit, H. Bowen; Anastassia, N. Alexandrova (2017). "SmB₆^– Cluster Anion: Covalency Involving f Orbitals". J. Phys. Chem. A 2017,^? 121,^? 8,^? 1849–1854. 121 (8): 1849–1854. doi:10.1021/acs.jpca.7b00247. PMID 28182423. S2CID 3723987..
^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 28. ISBN 978-0-08-037941-8.
^ Lide, D. R., ed. (2005). "Magnetic susceptibility of the elements and inorganic compounds". CRC Handbook of Chemistry and Physics (PDF) (86th ed.). Boca Raton (FL): CRC Press. p. 4-134. ISBN 0-8493-0486-5.
^ Weast, Robert (1983). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E112. ISBN 978-0-8493-0464-4.
^ Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
^ Chiera, Nadine M.; Sprung, Peter; Amelin, Yuri; Dressler, Rugard; Schumann, Dorothea; Talip, Zeynep (1 August 2024). "The ¹⁴⁶Sm half-life re-measured: consolidating the chronometer for events in the early Solar System". Scientific Reports. 14 (1). doi:10.1038/s41598-024-64104-6. PMC 11294585.
^ Cite error: The named reference emsley was invoked but never defined (see the help page).

[1] "Standard Atomic Weights: Samarium". CIAAW. 2005.

[CIAAW2021-2] Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; Böhlke, John K.; Chesson, Lesley A.; Coplen, Tyler B.; Ding, Tiping; Dunn, Philip J. H.; Gröning, Manfred; Holden, Norman E.; Meijer, Harro A. J. (2022-05-04). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.

[Arblaster_2018-3] Arblaster, John W. (2018). Selected Values of the Crystallographic Properties of Elements. Materials Park, Ohio: ASM International. ISBN 978-1-62708-155-9.

[Cloke1993-4] Yttrium and all lanthanides except Ce and Pm have been observed in the oxidation state 0 in bis(1,3,5-tri-t-butylbenzene) complexes, see Cloke, F. Geoffrey N. (1993). "Zero Oxidation State Compounds of Scandium, Yttrium, and the Lanthanides". Chem. Soc. Rev. 22: 17–24. doi:10.1039/CS9932200017. and Arnold, Polly L.; Petrukhina, Marina A.; Bochenkov, Vladimir E.; Shabatina, Tatyana I.; Zagorskii, Vyacheslav V.; Cloke (2003-12-15). "Arene complexation of Sm, Eu, Tm and Yb atoms: a variable temperature spectroscopic investigation". Journal of Organometallic Chemistry. 688 (1–2): 49–55. doi:10.1016/j.jorganchem.2003.08.028.

[5] SmB₆^- cluster anion has been reported and contains Sm in rare oxidation state of +1; see Paul, J. Robinson; Xinxing, Zhang; Tyrel, McQueen; Kit, H. Bowen; Anastassia, N. Alexandrova (2017). "SmB₆^– Cluster Anion: Covalency Involving f Orbitals". J. Phys. Chem. A 2017,^? 121,^? 8,^? 1849–1854. 121 (8): 1849–1854. doi:10.1021/acs.jpca.7b00247. PMID 28182423. S2CID 3723987..

[GE28-6] Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 28. ISBN 978-0-08-037941-8.

[magnet-7] Lide, D. R., ed. (2005). "Magnetic susceptibility of the elements and inorganic compounds". CRC Handbook of Chemistry and Physics (PDF) (86th ed.). Boca Raton (FL): CRC Press. p. 4-134. ISBN 0-8493-0486-5.

[8] Weast, Robert (1983). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E112. ISBN 978-0-8493-0464-4.

[NUBASE2020-9] Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.

[Chiera2024-10] Chiera, Nadine M.; Sprung, Peter; Amelin, Yuri; Dressler, Rugard; Schumann, Dorothea; Talip, Zeynep (1 August 2024). "The ¹⁴⁶Sm half-life re-measured: consolidating the chronometer for events in the early Solar System". Scientific Reports. 14 (1). doi:10.1038/s41598-024-64104-6. PMC 11294585.

[emsley-11] Cite error: The named reference emsley was invoked but never defined (see the help page).

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