Samarium

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| colspan="2" align="center" | Promethium – Samarium – Europium

Sm Pu
	Image:Sm-TableImage.png 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
Image:Sm,62.jpg 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

Electrical conductivity 0.956 10⁶/m ohm Thermal conductivity 13.3 W/(m

1^st ionization potential 544.5 kJ/mol 2^nd ionization potential 1070 kJ/mol 3^rd ionization potential 2260 kJ/mol 4^th ionization potential 3990 kJ/mol Most stable isotopes >¹⁴⁴Sm >3.07% >colspan="4" >¹⁴⁴Sm is stable with 82 neutrons >-

iso	NA	half-life	DM	DE MeV	DP >-	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

! colspan="2" align="center" bgcolor="#ffbfff" | 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.

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_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

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

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

External links

Category:Chemical elements Category:Lanthanides ca:Samari de:Samarium eo:Samario et:Samaarium es:Samario fr:Samarium it:Samario nl:Samarium ja:サマリウム pl:Samar pt:Samário ru:Самарий sl:Samarij sv:Samarium

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