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Samarium - Sm

CAS: 7440-19-9
Description:Silver-colored metal
Classification: Rare Earth (Lanthanide)
Date of Discovery: 1879
Discoverer: Paul Emile Lecoq de Boisbaudran
Name Origin: samarskite, a mineral

Atomic Number: 62
Number of Neutrons: 88
Atomic Mass: 150.36(3) amu
Melting Point: 1074 C
Boiling Point: 1794 C
Density @ 25 C: 7.520 g/cm3 alpha symbol
Atomic volume: 19.95 cm3/mol
Electrical resistivity: 0.00956 10-6/cm Ohm Symbol
Thermal conductivity: 0.133 W/cmK
Enthalpy of atomization: 209 kJ/mol (est.)
Enthalpy of vaporization: 166.40 kJ/mol
Enthalpy of fusion: 8.630 kJ/mol
Specific heat capacity: 0.20 J/gK
Energy levels: 2-8-18-24-8-2
Electron configuration: [Xe]4f 66s2
Crystal Structure: Rhombohedral
Atomic radius: 2.59
Covalent radius: 1.62
Oxidation States: +2, +3
Electronegativity, Pauling: 1.17
Electron affinity:
First ionization energy: 5.64 eV
2nd ionization energy: 11.069 eV
3rd ionization energy: 23.423 eV
Polarizability: 28.8 10-24cm3
Isotope Natural Abundance Atomic Mass Half-life Decay Mode Spin
131Sm 1.2 s Beta Symbol+, EC
133Sm 132.939 2.9 s Beta Symbol+, EC 5/2+
134Sm 133.934 11 s Beta Symbol+, EC 0+
135Sm 134.932 10 s Beta Symbol+, EC 7/2+
136Sm 135.9283 42 s Beta Symbol+, EC 0+
137Sm 136.9271 45 s Beta Symbol+, EC 0+
138Sm 137.9235 3.0 m Beta Symbol+, EC 0+
139mSm 10 s IT; Beta Symbol+ (11/2-)
139Sm 138.9226 2.6 m Beta Symbol+; EC 1/2+
140Sm 139.9195 14.8 m Beta Symbol+, EC 0+
141mSm 22.6 m Beta Symbol+; EC; IT 11/2-
141Sm 140.91847 10.2 m Beta Symbol+; EC 1/2+
142Sm 141.91520 1.208 h Beta Symbol+; EC 0+
143mSm 1.10 m IT 11/2-
143Sm 142.914624 8.83 m Beta Symbol+; EC 3/2+
144Sm 3.1(1) 143.911996 Stable 0+
145Sm 144.913407 340 d EC 7/2-
146Sm 145.913038 1.03 x 108 y alpha symbol- 0+
147Sm 15.0(2) 146.914894 1.06 x 1011 y alpha symbol- 7/2-
148Sm 11.3(1) 147.914818 7 x 1015 y alpha symbol- 0+
149Sm 13.8(1) 148.917180 1 x 1016 y alpha symbol- 7/2-
150Sm 7.4(1) 149.917272 Stable 0+
151Sm 150.919929 90 y Beta Symbol- 5/2-
152Sm 26.7(2) 151.919729 Stable 0+
153Sm 152.922094 1.929 d Beta Symbol- 3/2+
154Sm 22.7(2) 153.922206 Stable 0+
155Sm 154.924636 22.2 m Beta Symbol- 0+
156Sm 155.92553 9.4 h Beta Symbol- 0+
157Sm 156.9283 8.0 m Beta Symbol- 3/2-
158Sm 157.9299 5.5 m Beta Symbol- 0+
159Sm 158.9332 11.3 s Beta Symbol-
160Sm 159.9353 9.6 s Beta Symbol- 0+
Discovered spectroscopically by its sharp absorption lines in 1879 by Lecoq de Boisbaudran in the mineral samarskite, named in honor of a Russian mine official, Col. Samarski. Samarium is found along with other members of the rare-earth elements in many minerals, including monazite [(Nd,Ce,La,Pr,Sm,Gd)(P,Si)O4] and bastnasite, which are commercial sources. It occurs in monazite to the extent of 2.8%. While misch metal containing about 1% of samarium metal, has long been used, samarium has not been isolated in relatively pure form until recent years. Ion-exchange and solvent extraction techniques have recently simplified separation of the rare earths from one another; more recently, electrochemical deposition, using an electrolytic solution of lithium citrate and a mercury electrode, is said to be a simple, fast, and highly specific way to separate the rare earths. Samarium metal can be produced by reducing the oxide with barium or lanthanum. Samarium has a bright silver luster and is reasonably stable in air. Three crystal modifications of the metal exist, with transformations at 734 and 922 C. The metal ignites in air at about 150 C. Thirty-two isotopes and isomers of samarium are now recognized. Natural samarium is a mixture of seven isotopes, three of which are unstable but have long half-lives. Samarium, along with other rare-earths, is used for carbon-arc lighting for the motion picture industry. The sulfide has excellent high-temperature stability and good thermoelectric efficiencies up to 1100 C. SmCo5 has been used in making a new permanent magnet material with the highest resistance to demagnetization of any known material. It is said to have an intrinsic coercive force as high as 2200 kA/m. Samarium oxide has been used in optical glass to absorb the infrared. Samarium is used to dope calcium fluoride crystals for use in optical masers or lasers. Compounds of the metal act as sensitizers for phosphors excited in the infrared; the oxide exhibits catalytic properties in the dehydration and dehydrogenation of ethyl alcohol. It is used in infrared absorbing glass and as a neutron absorber in nuclear reactors. Little is known of the toxicity of samarium; therefore, it should be handled carefully.
LINKS:

Crystals of tris(tetramethylethylcyclopentadienyl)samarium
Information, data sheet and standard forms
Quadramet Samarium Sm-153 Lexidronam Injection
Samarium Cobalt Magnets
Samarium Cobalt Magnets 2
Samarium Laser Emits X-Rays


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Sources for the information on this website include:
Lide, David R., ed. CRC Handbook of Chemistry and Physics, 78th Ed., 1997-1998.