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Promethium - Samarium - Europium
Name, Symbol, NumberSamarium, Sm, 62
Chemical series Lanthanides
Group, Period, Block_ [?], 6 , f
Density, Hardness 7353 kg/m3, no data
Appearance silvery white
Atomic properties
Atomic weight 150.36(3) amu
Atomic radius (calc.) 185 (238) pm
Covalent radius no data
van der Waals radius no data
Electron configuration [Xe]6s²4f6
e- 's per energy level2, 8, 18, 24, 8, 2
Oxidation states (Oxide) 3 (mildly basic)
Crystal structure Rhombohedral[?]
Physical properties
State of matter solid (__)
Melting point 1345 K (1962 F)
Boiling point 2076 K (3277 F)
Molar volume 19.98 ×10-3 m3/mol
Heat of vaporization 166.4 kJ/mol
Heat of fusion 8.63 kJ/mol
Vapor pressure 563 Pa at 1345 K
Velocity of sound 2130 m/s at 293.15 K
Electronegativity 1.17 (Pauling scale)
Specific heat capacity 200 J/(kg*K)
Electrical conductivity 0.956 106/m ohm
Thermal conductivity 13.3 W/(m*K)
1st ionization potential 544.5 kJ/mol
2nd ionization potential 1070 kJ/mol
3rd ionization potential 2260 kJ/mol
4th ionization potential 3990 kJ/mol
Most stable isotopes
isoNAhalf-life DMDE MeVDP
144Sm3.07%144Sm is stable with 82 neutrons
146Sm{syn.}1.03E+8 a α2.529142Nd
147Sm14.99%1.06E+11 a α2.310143Nd
148Sm11.24%7E+15 aα1.986144Nd
149Sm13.82%>2E+15 aαno data145Nd
150Sm7.38%150Sm is stable with 88 neutrons
152Sm26.75%150Sm is stable with 90 neutrons
154Sm22.75%150Sm is stable with 92 neutrons
SI units & STP are used except where noted.
Samarium is a chemical element in the periodic table that has the symbol Sm and atomic number 62.

Table of contents

Notable characteristics

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


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 oxide is used in optical glass to absorb infrared light.
  • Samarium compounds act as sensitizers for phosphors excited in the infrared.
  • Samarium oxide is catalytic for the dehydration and dehydrogenation of ethanol.


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, it was named after a Russian mine official, Colonel Samarski.

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[?]. Samarium can also be obtained by reducing its oxide with Lanthanum.


Compounds of Samarium include:


Naturally occurring Samarium is composed of 4 stable isotopes, 144-Sm, 150-Sm, 152-Sm and 154-Sm, and 3 radioisotopes, 147-Sm, 148-Sm and 149-Sm, with 152-Sm being the most abundant (26.75% natural abundance). 32 radioisotopes have been characterized, with the most stable being 148-Sm with a half-life of 7E+15 years, 149-Sm with a half-life of more than 2E+15 years, and 147-Sm with a half-life of 1.06E+11 years. All of the remaining radioactive isotopes have half-lifes that are less than 1.04E+8 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 141m-Sm (t 22.6 minutes), 143m1-Sm (t 66 seconds) and 139m-Sm (t 10.7 seconds).

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


All Samarium compounds should be regarded as highly toxic; Samarium compounds are skin and eye irritants, and the metal dust presents a fire and explosion hazard.

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