Samarium

Chemical element, symbol Sm and atomic number 62 / From Wikipedia, the free encyclopedia

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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.

Quick facts: Samarium, Pronunciation, Appearance, Standard...
Samarium, 62Sm
Samarium-2.jpg
Samarium
Pronunciation/səˈmɛəriəm/ (sə-MAIR-ee-əm)
Appearancesilvery white
Standard atomic weight Ar°(Sm)
Samarium in the periodic table


Sm

Pu
promethiumsamariumeuropium
Atomic number (Z)62
Groupf-block groups (no number)
Periodperiod 6
Block  f-block
Electron configuration[Xe] 4f6 6s2
Electrons per shell2, 8, 18, 24, 8, 2
Physical properties
Phase at STPsolid
Melting point1345 K (1072 °C, 1962 °F)
Boiling point2173 K (1900 °C, 3452 °F)
Density (near r.t.)7.52 g/cm3
when liquid (at m.p.)7.16 g/cm3
Heat of fusion8.62 kJ/mol
Heat of vaporization192 kJ/mol
Molar heat capacity29.54 J/(mol·K)
Vapor pressure
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 1001 1106 1240 (1421) (1675) (2061)
Atomic properties
Oxidation states0,[3] +1,[4] +2, +3 (a mildly basic oxide)
ElectronegativityPauling scale: 1.17
Ionization energies
  • 1st: 544.5 kJ/mol
  • 2nd: 1070 kJ/mol
  • 3rd: 2260 kJ/mol
Atomic radiusempirical: 180 pm
Covalent radius198±8 pm
Color lines in a spectral range
Spectral lines of samarium
Other properties
Natural occurrenceprimordial
Crystal structure rhombohedral
Rhombohedral crystal structure for samarium
Thermal expansionα, poly: 12.7 (at r.t.) µm/(m⋅K)
Thermal conductivity13.3 W/(m⋅K)
Electrical resistivityα, poly: 0.940 (at r.t.) µΩ⋅m
Magnetic orderingparamagnetic[5]
Molar magnetic susceptibility+1860.0×10−6 cm3/mol (291 K)[6]
Young's modulusα form: 49.7 GPa
Shear modulusα form: 19.5 GPa
Bulk modulusα form: 37.8 GPa
Speed of sound thin rod2130 m/s (at 20 °C)
Poisson ratioα form: 0.274
Vickers hardness410–440 MPa
Brinell hardness440–600 MPa
CAS Number7440-19-9
History
Namingafter the mineral samarskite (itself named after Vassili Samarsky-Bykhovets)
Discovery and first isolationLecoq de Boisbaudran (1879)
Isotopes of samarium
Main isotopes[7] Decay
abun­dance half-life (t1/2) mode pro­duct
144Sm 3.08% stable
145Sm synth 340 d ε 145Pm
146Sm trace 1.03×108 y α 142Nd
147Sm 15% 1.07×1011 y α 143Nd
148Sm 11.3% 6.3×1015 y α 144Nd
149Sm 13.8% stable
150Sm 7.37% stable
151Sm synth 94.6 y β 151Eu
152Sm 26.7% stable
153Sm synth 46.28 h β 153Eu
154Sm 22.7% stable
Symbol_category_class.svg Category: Samarium
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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, albeit indirectly.

Samarium is the 40th most abundant element in Earth's crust and more common than metals such as tin. It 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,[8] 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.[9]

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