Samarium

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

Atomic volume: 19.95 cm³/mol
Electrical resistivity: 0.00956 10^-6/cm

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 Å
Covalent radius: 1.62 Å
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	⁺, EC
¹³³Sm	132.939	2.9 s	⁺, EC	5/2+
¹³⁴Sm	133.934	11 s	⁺, EC	0+
¹³⁵Sm	134.932	10 s	⁺, EC	7/2+
¹³⁶Sm	135.9283	42 s	⁺, EC	0+
¹³⁷Sm	136.9271	45 s	⁺, EC	0+
¹³⁸Sm	137.9235	3.0 m	⁺, EC	0+
^139mSm	10 s	IT; ⁺	(11/2-)
¹³⁹Sm	138.9226	2.6 m	⁺; EC	1/2+
¹⁴⁰Sm	139.9195	14.8 m	⁺, EC	0+
^141mSm	22.6 m	⁺; EC; IT	11/2-
¹⁴¹Sm	140.91847	10.2 m	⁺; EC	1/2+
¹⁴²Sm	141.91520	1.208 h	⁺; EC	0+
^143mSm	1.10 m	IT	11/2-
¹⁴³Sm	142.914624	8.83 m	⁺; 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	^-	0+
¹⁴⁷Sm	15.0(2)	146.914894	1.06 x 10¹¹ y	^-	7/2-
¹⁴⁸Sm	11.3(1)	147.914818	7 x 10¹⁵ y	^-	0+
¹⁴⁹Sm	13.8(1)	148.917180	1 x 10¹⁶ y	^-	7/2-
¹⁵⁰Sm	7.4(1)	149.917272	Stable	0+
¹⁵¹Sm	150.919929	90 y	^-	5/2-
¹⁵²Sm	26.7(2)	151.919729	Stable	0+
¹⁵³Sm	152.922094	1.929 d	^-	3/2+
¹⁵⁴Sm	22.7(2)	153.922206	Stable	0+
¹⁵⁵Sm	154.924636	22.2 m	^-	0+
¹⁵⁶Sm	155.92553	9.4 h	^-	0+
¹⁵⁷Sm	156.9283	8.0 m	^-	3/2-
¹⁵⁸Sm	157.9299	5.5 m	^-	0+
¹⁵⁹Sm	158.9332	11.3 s	^-
¹⁶⁰Sm	159.9353	9.6 s	^-	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 Return Sources for the information on this website include: Lide, David R., ed. CRC Handbook of Chemistry and Physics, 78th Ed., 1997-1998.

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