|Name, Symbol, Number||samarium, Sm, 62|
|Group, Period, Block||n/a, 6, f|
|Atomic mass||150.36(2) g/mol|
|Electron configuration||[Xe] 4f6 6s2|
|Electrons per shell||2, 8, 18, 24, 8, 2|
|Density (near r.t.)||7.52 g/cm³|
|Liquid density at m.p.||7.16 g/cm³|
|Melting point||1345 K
(1072 °C, 1962 °F)
|Boiling point||2067 K
(1794 °C, 3261 °F)
|Heat of fusion||8.62 kJ/mol|
|Heat of vaporization||165 kJ/mol|
|Heat capacity||(25 °C) 29.54 J/(mol·K)|
(mildly basic oxide)
|Electronegativity||1.17 (Pauling scale)|
|1st: 544.5 kJ/mol|
|2nd: 1070 kJ/mol|
|3rd: 2260 kJ/mol|
|Atomic radius||185 pm|
|Atomic radius (calc.)||238 pm|
|Electrical resistivity||(r.t.) (α, poly) 0.940 µΩ·m|
|Thermal conductivity||(300 K) 13.3 W/(m·K)|
|Thermal expansion||(r.t.) (α, poly)
|Speed of sound (thin rod)||(20 °C) 2130 m/s|
|Speed of sound (thin rod)||(r.t.) (α form) 49.7 m/s|
|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|
Samarium is never found free in nature, but, like other rare earth elements, it is contained in many minerals, including monazite, bastnasite and samarskite. Of these, monazite (in which it occurs up to an extent of 2.8 percent) and bastnasite are also used as commercial sources.
Misch metal containing about one percent 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 (Greenwood and Earnshaw 1998). Samarium can also be obtained by reducing its oxide with lanthanum.
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.
Samarium is an inner transition metal (or lanthanide) that lies in period six of the periodic table, between promethium and europium. It is reasonably stable in air at ordinary temperatures, but it ignites in air at 150 °C. Even with long-term storage under mineral oil, samarium is gradually oxidized to form a grayish-yellow powder of the oxide-hydroxide. Three crystal modifications of the metal also exist, with transformations at 734 and 922 °C.
Naturally occurring samarium is composed of four stable isotopes, 144Sm, 150Sm, 152Sm and 154Sm, and three radioisotopes, 147Sm, 148Sm and 149Sm, with 152Sm being the most abundant (26.75 percent 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 five meta states with the most stable being 141mSm (t½ 22.6 minutes), 143m1Sm (t½ 66 seconds) and 139mSm (t½ 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.
Compounds of Samarium include:
Uses of Samarium include:
As with the other lanthanides, samarium compounds are thought to have low to moderate toxicity, although their toxicity has not been investigated in detail.
All links retrieved August 12, 2015.
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