Samarium

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] 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
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
Main article: Isotopes of samarium iso NA half-life DM DE (MeV) DP 144Sm 3.07% Sm is stable with 82 neutrons 146Sm syn 1.03×108y α 2.529 142Nd 147Sm 14.99% 1.06×1011y α 2.310 143Nd 148Sm 11.24% 7×1015y 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
References

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

Notable characteristics

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 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".

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).

The samarskite mineral was named after Vasili Samarsky-Bykhovets, the Chief of Staff (Colonel) of the Russian Corps of Mining Engineers in 1845–1861. The name of the element is derived from the name of the mineral, and thus traces back to the name Samarsky-Bykhovets. In this sense samarium was the first chemical element to be named after a living person.

Biological role

Samarium has no known biological role, but is said to stimulate the metabolism.^{[citation needed]}

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

See also samarium compounds.

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 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 (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.

References

• Los Alamos National Laboratory – Samarium
• Centerwatch About drug Quadramet

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

External links

• WebElements.com – Samarium
• It's Elemental – Samarium
• Reducing Agents > Samarium low valent