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62 promethiumsamariumeuropium


periodic table
Name, Symbol, Number samarium, Sm, 62
Chemical series lanthanides
Group, Period, Block n/a, 6, f
Appearance silvery white
Atomic mass 150.36(2) g/mol
Electron configuration [Xe] 4f6 6s2
Electrons per shell 2, 8, 18, 24, 8, 2
Physical properties
Phase solid
Density (near r.t.) 7.52 g/cm³
Liquid density at m.p. 7.16 g/cm³
Melting point 1345 K
(1072 °C, 1962 °F)
Boiling point 2067 K
(1794 °C, 3261 °F)
Heat of fusion 8.62 kJ/mol
Heat of vaporization 165 kJ/mol
Heat capacity (25 °C) 29.54 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
Crystal structure rhombohedral
Oxidation states 3
(mildly basic oxide)
Electronegativity 1.17 (Pauling scale)
Ionization energies
1st: 544.5 kJ/mol
2nd: 1070 kJ/mol
3rd: 2260 kJ/mol
Atomic radius 185 pm
Atomic radius (calc.) 238 pm
Magnetic ordering antiferromagnetic
Electrical resistivity (r.t.) (α, poly) 0.940 µΩ·m
Thermal conductivity (300 K) 13.3 W/(m·K)
Thermal expansion (r.t.) (α, poly)
12.7 µm/(m·K)
Speed of sound (thin rod) (20 °C) 2130 m/s
Speed of sound (thin rod) (r.t.) (α form) 49.7 m/s
Shear modulus (α form) 19.5 GPa
Bulk modulus (α form) 37.8 GPa
Poisson ratio (α form) 0.274
Vickers hardness 412 MPa
Brinell hardness 441 MPa
CAS registry number 7440-19-9
Notable isotopes
Main article: Isotopes of samarium
iso NA half-life DM DE (MeV) DP
144Sm 3.07% Sm is stable with 82 neutrons
146Sm syn 1.03×108y α 2.529 142Nd
147Sm 14.99% 1.06×1011y α 2.310 143Nd
148Sm 11.24% 7×1015y α 1.986 144Nd
149Sm 13.82% >2×1015 y α 1.870 145Nd
150Sm 7.38% Sm is stable with 88 neutrons
152Sm 26.75% Sm is stable with 90 neutrons
154Sm 22.75% Sm is stable with 92 neutrons

Samarium (chemical symbol Sm, atomic number 62) is a bright silvery metal that is a member of the lanthanide series of chemical elements. It is considered one of the "rare earth metals."[1]


Samarium is never found free in nature, but, like other rare earth elements, it is contained in many minerals, including monazite, bastnasite and samarskite. Of these, monazite (in which it occurs up to an extent of 2.8 percent) and bastnasite are also used as commercial sources.

Misch metal containing about one percent of samarium has long been used, but it was not until recent years that relatively pure samarium has been isolated through ion exchange processes, solvent extraction techniques, and electrochemical deposition. The metal is often prepared by electrolysis of a molten mixture of samarium(III) chloride with sodium chloride or calcium chloride (Greenwood and Earnshaw 1998). Samarium can also be obtained by reducing its oxide with lanthanum.


Samarium was first discovered spectroscopically in 1853 by Swiss chemist Jean Charles Galissard de Marignac by its sharp absorption lines in didymium, and isolated in Paris in 1879 by French chemist Paul Émile Lecoq de Boisbaudran from the mineral samarskite ((Y,Ce,U,Fe)3(Nb,Ta,Ti)5O16).

The samarskite mineral was named after Vasili Samarsky-Bykhovets, the Chief of Staff (Colonel) of the Russian Corps of Mining Engineers in 1845–1861. The name of the element is derived from the name of the mineral, and thus traces back to the name Samarsky-Bykhovets. In this sense samarium was the first chemical element to be named after a living person.

Notable characteristics

Samarium is an inner transition metal (or lanthanide) that lies in period six of the periodic table, between promethium and europium. It is reasonably stable in air at ordinary temperatures, but it ignites in air at 150 °C. Even with long-term storage under mineral oil, samarium is gradually oxidized to form a grayish-yellow powder of the oxide-hydroxide. Three crystal modifications of the metal also exist, with transformations at 734 and 922 °C.


Naturally occurring samarium is composed of four stable isotopes, 144Sm, 150Sm, 152Sm and 154Sm, and three radioisotopes, 147Sm, 148Sm and 149Sm, with 152Sm being the most abundant (26.75 percent natural abundance). 32 radioisotopes have been characterized, with the most stable being 148Sm with a half-life of 7x1015 years, 149Sm with a half-life of more than 2x1015 years, and 147Sm with a half-life of 1.06x1011 years. All of the remaining radioactive isotopes have half-lifes that are less than 1.04x108 years, and the majority of these have half lifes that are less than 48 seconds. This element also has five meta states with the most stable being 141mSm (t½ 22.6 minutes), 143m1Sm (t½ 66 seconds) and 139mSm (t½ 10.7 seconds).

The primary decay mode before the most abundant stable isotope, 152Sm, is electron capture, and the primary mode after is beta minus decay. The primary decay products before 152Sm are element Pm (promethium) isotopes, and the primary products after are element Eu (europium) isotopes.


Compounds of Samarium include:


Uses of Samarium include:

  • Carbon-arc lighting for the motion picture industry (together with other rare earth metals).
  • Doping CaF2 crystals for use in optical masers or lasers.
  • As a neutron absorber in nuclear reactors.
  • For alloys and headphones.
  • Samarium-Cobalt magnets; SmCo5 and Sm2Co17 are used in making permanent magnet materials that have high resistance to demagnetization when compared to other permanent magnet materials.
  • Samarium(II) iodide is used as a chemical reagent in organic synthesis, for example in the Barbier reaction.
  • Samarium oxide is used in optical glass to absorb infrared light.
  • Samarium compounds act as sensitizers for phosphors excited in the infrared.
  • Samarium oxide is a catalyst for the dehydration and dehydrogenation of ethanol.
  • Radioactive Samarium-153 is used in medicine to treat the severe pain associated with cancers that have spread to bone. The drug is called "Quadramet."


As with the other lanthanides, samarium compounds are thought to have low to moderate toxicity, although their toxicity has not been investigated in detail.

See also


  1. The term "rare earth metals" (or "rare earth elements") is a trivial name applied to 16 chemical elements: scandium, yttrium, and 14 of the 15 lanthanides (excluding promethium), which occur naturally on Earth. Some definitions also include the actinides. The word "earth" is an obsolete term for oxide. The term "rare earth" is discouraged by the International Union of Pure and Applied Chemistry (IUPAC), as these elements are relatively abundant in the Earth's crust.

ISBN links support NWE through referral fees

  • Chang, Raymond. 2006. Chemistry. 9th ed. New York: McGraw-Hill Science/Engineering/Math. ISBN 0073221031
  • Cotton, F. Albert, and Geoffrey Wilkinson. 1980. Advanced Inorganic Chemistry. 4th ed. New York: Wiley. ISBN 0-471-02775-8
  • Greenwood, N.N. and A. Earnshaw. 1998. Chemistry of the Elements. 2nd ed. Oxford, U.K.; Burlington, MA: Butterworth-Heinemann, Elsevier Science. ISBN 0750633654 Online version Retrieved October 20, 2007.
  • Jones, Adrian P., Frances Wall, and C. Terry Williams, eds. 1996. Rare Earth Minerals: Chemistry, Origin and Ore Deposits. The Mineralogical Society Series. London, UK: Chapman and Hall. ISBN 0412610302
  • "Samarium" Los Alamos National Laboratory, Chemistry Division. Retrieved October 20, 2007.
  • Stwertka, Albert. 1998. Guide to the Elements. Rev. ed. Oxford, UK: Oxford University Press. ISBN 0-19-508083-1

External links

All links retrieved December 22, 2022.


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