Samarium

Promethium – Samarium – Europium Sm Pu       Full table
General
Name, Symbol, Number	Samarium, 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 level	2, 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 ×10-6 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
Miscellaneous
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
iso NA half-life DM DE MeV DP 144Sm 3.07% 144Sm is stable with 82 neutrons 146Sm {syn.} 1.03E+8 y α 2.529 142Nd 147Sm 14.99% 1.06E+11 y α 2.310 143Nd 148Sm 11.24% 7E+15 y α 1.986 144Nd 149Sm 13.82% >2E+15 y α no data 145Nd 150Sm 7.38% 150Sm is stable with 88 neutrons 152Sm 26.75% 150Sm is stable with 90 neutrons 154Sm 22.75% 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.

Contents

1 Notable characteristics 2 Applications 3 History 4 Biological role 5 Occurrence 6 Compounds 7 Isotopes 8 Precautions 9 References 10 External links

Notable characteristics

Samarium is a rare earth metal, with a 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 a catalyst 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. The metal is often prepared by electrolysis of a molten mixture of samarium(III) chloride with sodium chloride or calcium chloride^[1]. 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_? 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.

Precautions

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

References

• Los Alamos National Laboratory – Samarium (http://periodic.lanl.gov/elements/62.html)

1. N. N. Greenwood, A. Earnshaw, Chemistry of the Elements, Pergamon Press, Oxford, UK, 1984.

External links

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