Chemical Properties
silvery grey powder
Physical properties
Samarium is a hard, brittle, silver-white metal. When freshly cut, it does not tarnish significantlyunder normal room temperature conditions. Four of its isotopes are radioactive andemit alpha particles (helium nuclei). They are Sm-146, Sm-147, Sm-148, and Sm-149.
Its melting point is 1,074°C, its boiling point is 1,794°C, and its density is 7.52g.cm3.
Isotopes
There are 41 known isotopes of samarium. Seven of these are consideredstable. Sm-144 makes up just 3.07% of the natural occurring samarium, Sm-150 makesup 7.38% of natural samarium found on Earth, Sm-152 constitutes 26.75%, and Sm-154 accounts for 22.75%. All the remaining isotopes are radioactive and have very longhalf-lives; therefore, they are considered “stable.” All three contribute to the natural occurrenceof samarium: Sm-147 = 14.99%, Sm-148 = 11.24%, and Sm-149 = 13.82%.
Samarium is one of the few elements with several stable isotopes that occur naturallyon Earth.
Origin of Name
It is named after the mineral samarskite.
Occurrence
Samarium is the 39th most abundant element in the Earth’s crust and the fifth in abundance(6.5 ppm) of all the rare-earths. In 1879 samarium was first identified in the mineralsamarskite [(Y, Ce U, Fe)3 (Nb, Ta, Ti5)O16]. Today, it is mostly produced by the ion-exchangeprocess from monazite sand. Monazite sand contains almost all the rare-earths, 2.8% of whichis samarium. It is also found in the minerals gadolinite, cerite, and samarskite in South Africa,South America, Australia, and the southeastern United States. It can be recovered as a byproductof the fission process in nuclear reactors.
Characteristics
Samarium is somewhat resistant to oxidation in air but will form a yellow oxide over time. Itignites at the rather low temperature of 150°C. It is an excellent reducing agent, releases hydrogenwhen immersed in water, and has the capacity to absorb neutrons in nuclear reactors.
Definition
A silvery element
of the lanthanoid series of metals. It
occurs in association with other lanthanoids.
Samarium is used in the metallurgical,
glass, and nuclear industries.
Symbol: Sm; m.p. 1077°C; b.p.
1791°C; r.d. 7.52 (20°C); p.n. 62; r.a.m.
150.36.
Definition
samarium: Symbol Sm. A soft silverymetallic element belonging tothe lanthanoids; a.n. 62; r.a.m.150.35; r.d. 7.52 (20°C); m.p. 1077°C;b.p. 1791°C. It occurs in monaziteand bastnatite. There are seven naturallyoccurring isotopes, all of whichare stable except samarium–147,which is weakly radioactive (half-life2.5 × 1011 years). The metal is usedin special alloys for making nuclearreactorparts as it is a neutron absorber.Samarium oxide (Sm2O3) isused in small quantities in special opticalglasses. The largest use of the elementis in the ferromagnetic alloySmCo5, which produces permanentmagnets five times stronger than anyother material. The element was discoveredby Fran?ois Lecoq de Boisbaudranin 1879.
Hazard
The salts of samarium are toxic if ingested. These salts react with water, liberating hydrogen,which may explode.
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