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62 promethiumsamariumeuropium


Periodic Table - Extended 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·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
Heat capacity (25 °C) 29.54 J·mol−1·K−1
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
( more)
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
Electrical resistivity ( r.t.) (α, poly) 0.940 µΩ·m
Thermal conductivity (300 K) 13.3 W·m−1·K−1
Thermal expansion ( r.t.) (α, poly)
12.7 µm/(m·K)
Speed of sound (thin rod) (20 °C) 2130 m/s
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 1.03×108 y α 2.529 142Nd
147Sm 14.99% 1.06×1011 y α 2.310 143Nd
148Sm 11.24% 7×1015 y 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 ( IPA: /səˈmɛːriəm/) is a chemical element in the periodic table that has the symbol Sm and atomic number 62.

Notable characteristics


Samarium is a rare earth metal, with a bright silver luster, that is reasonably stable in air; it ignites in air at 150 ° C. Three crystal modifications of the metal also exist, with transformations at 734 and 922 °C.


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 is used in making a new permanent magnet material with the highest resistance to demagnetization of any known material, and an intrinsic coercive force as high as 2200 kA/m.
  • 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).

Like the mineral, Samarium was named after a Vasili Samarsky-Bykhovets (Василий Евграфович Самарский-Быховец, Vasilij Evgrafovič Samarskij-Byhovec - 1803-1870), who was from 1845 through 1861 the Chief of Staff (Colonel) of the Russian Corps of Mining Engineers. He granted Rose to study the samples of the black mineral from Ural mountains.

Samarium is the first chemical element named after a person.

Biological role

Samarium has no known biological role, but is said to stimulate the metabolism.


Samarium is never found free in nature, but, like other rare earth elements, is contained in many minerals, including monazite, bastnasite and samarskite; monazite (in which it occurs up to an extent of 2.8%) and bastnasite are also used as commercial sources. Misch metal containing about 1% 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. Samarium can also be obtained by reducing its oxide with lanthanum.


Compounds of Samarium include:

  • Fluorides
    • SmF2
    • SmF3
  • Chlorides
    • SmCl2
    • SmCl3
  • Bromides
    • SmBr2
    • SmBr3
  • Iodides
    • SmI2
    • SmI3
  • Oxides
    • Sm2O3
  • Sulfides
    • Sm2S3
  • Selenides
    • Sm2Se3
  • Tellurides
    • Sm2Te3


Naturally occurring samarium is composed of 4 stable isotopes, 144Sm, 150Sm, 152Sm and 154Sm, and 3 radioisotopes, 147Sm, 148Sm and 149Sm, with 152Sm being the most abundant (26.75% 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 5 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.


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

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