Samarium Information
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Samarium Element
Samarium is a chemical element
with the symbol Sm and atomic number 62. It is a moderately hard silvery metal
that slowly oxidizes in air. Being a typical member of the lanthanide series,
samarium usually assumes the oxidation state +3. Compounds of samarium(II) are
also known, most notably the monoxide SmO, monochalcogenides SmS, SmSe and
SmTe, as well as samarium(II) iodide. The last compound is a common reducing
agent in chemical synthesis. Samarium has no significant biological role but is
only slightly toxic.
Samarium is a moderately soft
metal, silvery white in colour. It is relatively stable in air, slowly
oxidizing to Sm2O3. It rapidly dissolves in diluted acids—except hydrofluoric
acid (HF), in which it is stable because of formation of a protective
trifluoride (SmF3) layer. Samarium is a moderately strong paramagnet above 109
K (−164 °C, or −263 °F). Below 109 K, antiferromagnetic order develops for the
cubic sites in the samarium lattice, and the hexagonal site atoms finally order
antiferromagnetically below 14 K (−259 °C, or −434 °F).
Samarium was isolated as an
impure oxide and spectroscopically identified as a new element in 1879 by
French chemist Paul-Émile Lecoq de Boisbaudran. Samarium occurs in many other
rare-earth minerals but is almost exclusively obtained from bastnasite; it is
also found in products of nuclear fission. In Earth’s crust, samarium is as
abundant as tin.
Samarium was discovered in 1879
by the French chemist Paul-Émile Lecoq de Boisbaudran and named after the
mineral samarskite from which it was isolated. The mineral itself was earlier
named after a Russian mine official, Colonel Vassili Samarsky-Bykhovets, who
thereby became the first person to have a chemical element named after him,
albeit indirectly. Although classified as a rare-earth element, samarium is the
40th most abundant element in the Earth's crust and is more common than metals
such as tin. Samarium occurs with concentration up to 2.8% in several minerals
including cerite, gadolinite, samarskite, monazite and bastnäsite, the last two
being the most common commercial sources of the element. These minerals are
mostly found in China, the United States, Brazil, India, Sri Lanka and
Australia; China is by far the world leader in samarium mining and production.
The major commercial application
of samarium is in samarium–cobalt magnets, which have permanent magnetization
second only to neodymium magnets; however, samarium compounds can withstand
significantly higher temperatures, above 700 °C (1,292 °F), without losing
their magnetic properties, due to the alloy's higher Curie point. The
radioactive isotope samarium-153 is the active component of the drug samarium
(153Sm) lexidronam (Quadramet), which kills cancer cells in the treatment of
lung cancer, prostate cancer, breast cancer and osteosarcoma. Another isotope,
samarium-149, is a strong neutron absorber and is therefore added to the
control rods of nuclear reactors. It is also formed as a decay product during
the reactor operation and is one of the important factors considered in the reactor
design and operation. Other applications of samarium include catalysis of
chemical reactions, radioactive dating and X-ray lasers.
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