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Samarium

2007 Schools Wikipedia Selection. Related subjects: Chemical elements


                62            promethium ← samarium → europium
                 -
                ↑
                Sm
                ↓
                Pu

                                  Periodic Table - Extended Periodic Table

                                                                   General
                                     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] 4f^6 6s^2
                                    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

   CAPTION: 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
                                                             Miscellaneous
                                       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

                 CAPTION: Main article: Isotopes of samarium

                             iso     NA    half-life   DM DE ( MeV)   DP
                            ^144Sm 3.07%  Sm is stable with 82 neutrons
                            ^146Sm syn    1.03×10^8 y  α  2.529     ^142Nd
                            ^147Sm 14.99% 1.06×10^11 y α  2.310     ^143Nd
                            ^148Sm 11.24% 7×10^15 y    α  1.986     ^144Nd
                            ^149Sm 13.82% >2×10^15 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

                                                                References

   Samarium ( IPA: /səˈmɛːriəm/) is a chemical element in the periodic
   table that has the symbol Sm and atomic number 62.

Notable characteristics

   Samarium
   Enlarge
   Samarium

   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.

Applications

   Uses of Samarium include:
     * Carbon-arc lighting for the motion picture industry (together with
       other rare earth metals).
     * Doping CaF[2] crystals for use in optical masers or lasers.
     * As a neutron absorber in nuclear reactors.
     * For alloys and headphones.
     * Samarium-Cobalt magnets; SmCo[5] 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".

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)[5]O[16]).

   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.

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. 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

   Compounds of Samarium include:
     * Fluorides
          + SmF[2]
          + SmF[3]
     * Chlorides
          + SmCl[2]
          + SmCl[3]
     * Bromides
          + SmBr[2]
          + SmBr[3]
     * Iodides
          + SmI[2]
          + SmI[3]
     * Oxides
          + Sm[2]O[3]
     * Sulfides
          + Sm[2]S[3]
     * Selenides
          + Sm[2]Se[3]
     * Tellurides
          + Sm[2]Te[3]

Isotopes

   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 7x10^15 years, ^149Sm with a half-life of
   more than 2x10^15 years, and ^147Sm with a half-life of 1.06x10^11
   years. All of the remaining radioactive isotopes have half-lifes that
   are less than 1.04x10^8 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 ^141mSm (t[½] 22.6 minutes), ^143m1Sm
   (t[½] 66 seconds) and ^139mSm (t[½] 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.

Precautions

   As with the other lanthanides, samarium compounds are of low to
   moderate toxicity, although their toxicity has not been investigated in
   detail.
   Retrieved from " http://en.wikipedia.org/wiki/Samarium"
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   with only minor checks and changes (see www.wikipedia.org for details
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