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62 promethiumsamariumeuropium


Name, Symbol, Number samarium, Sm, 62
Chemical series lanthanides
Group, Period, Block n/a, 6, f
Appearance silvery white
Standard atomic weight 150.36(2)  g·mol−1
Electron configuration [Xe] 4f6 6s2
Physical properties
Phase solid
Density (near r.t.) 7.52  g·cm−3
Liquid density at m.p. 7.16  g·cm−3
Melting point 1345 K
(1072 °C, 1962 °F)
Boiling point 2067 K
(1794 °C, 3261 °F)
Heat of fusion 8.62  kJ·mol−1
Heat of vaporization 165  kJ·mol−1
Vapor pressure
Atomic properties
Crystal structure rhombohedral
Oxidation states 3
(mildly basic oxide)
Electronegativity 1.17 (Pauling scale)
Ionization energies
1st:  544.5  kJ·mol−1
2nd:  1070  kJ·mol−1
3rd:  2260  kJ·mol−1
Atomic radius 185  pm
Atomic radius (calc.) 238  pm
Magnetic ordering antiferromagnetic
Thermal expansion (r.t.) (α, poly)
12.7 µm/(m·K)
Young's modulus (α form) 49.7  GPa
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
Selected 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 (pronounced /səˈmɛəriəm/) is a chemical element with the symbol Sm and atomic number 62.

Additional recommended knowledge


Notable characteristics




Uses of Samarium include:

  • Carbon-arc lighting for the motion picture industry (together with other rare earth metals).
  • 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. These materials have high coercivities and intrinsic coercivities. Samarium-cobalt combinations have recently found use in high-end magnetic pickups for guitars and related musical instruments.
  • 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".


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). Although samarskite was first found in the Urals, by the late 1870s a new deposit had been located in North Carolina, and it was from that source that the samarium-bearing didymium had originated.


Prior to the advent of ion-exchange separation technology in the 1950s, samarium had no commercial uses in pure form. However, a by-product of the fractional crystallization purification of neodymium was a mixture of samarium and gadolinium that acquired the name of "Lindsay Mix" after the company that made it. This material is thought to have been used for nuclear control rods in some of the early nuclear reactors. Nowadays, a similar commodity product goes under the name of "Samarium-Europium-Gadolinium" concentrate (or SEG concentrate). This is prepared by solvent extraction from the mixed lanthanides extracted from bastnäsite (or monazite). Since the heavier lanthanides have the greater affinity for the solvent used, they are easily extracted from the bulk using relatively small proportions of solvent. Not all rare earth producers who process bastnäsite do so on large enough scale to continue onward with the separation of the components of SEG, which typically makes up only one or two percent of the original ore. Such producers will therefore be making SEG with a view to marketing it to the specialized processors. In this manner, the valuable europium content of the ore is rescued for use in phosphor manufacture. Samarium purification follows the removal of the europium. Currently, being in oversupply, samarium oxide is less expensive on a commercial scale than its relative abundance in the ore might suggest.

Biological role





Compounds of Samarium include:

See also samarium compounds.


Main article: isotopes of samarium

Naturally occurring samarium is composed of 4 stable isotopes, 144Sm, 150Sm, 152Sm and 154Sm, and 3 extremely long-lived radioisotopes, 147Sm (1.06×1011y), 148Sm (7×1015y) and 149Sm (>2×1015y), with 152Sm being the most abundant (26.75% natural abundance).

151Sm has a halflife of 90 years, and 145Sm has a halflife of 340 days. All of the remaining radioisotopes have half-lives that are less than 2 days, and the majority of these have half-lives that are less than 48 seconds. This element also has 5 meta states with the most stable being 141mSm (t½ 22.6 minutes), 143m1Sm (t½ 66 seconds) and 139mSm (t½ 10.7 seconds).


Natural Samarium has an activity of 128 Bq/g.




  • Los Alamos National Laboratory – Samarium
  • Centerwatch About drug Quadramet
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Samarium". A list of authors is available in Wikipedia.