Samarium

Notable characteristics

Samarium is a rare earth metal, witha bright silver lustre, 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, respectively.

Applications

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.

History

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.

Occurrence

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

Compounds of Samarium include:

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

Isotopes

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_½ 22.6 minutes), 143m1-Sm (t_½ 66 seconds) and 139m-Sm (t_½ 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.

Precautions

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.

External links

• WebElements.com - Samarium (http://www.webelements.com/webelements/elements/text/Sm/index)
• EnvironmentalChemistry.com - Samarium (http://environmentalchemistry.com/yogi/periodic/Sm)
• It's Elemental - Samarium (http://education.jlab.org/itselemental/ele062)