Samarium Facts – Sm or Atomic Number 62


Samarium Facts
Samarium is a rare earth element with symbol Sm and atomic number 62.

Samarium is a chemical element with the symbol Sm and atomic number 62. This metal is a member of the lanthanide series on the periodic table. Although the “rare earths” is another name for the lanthanides series, samarium is not actually that rare.

Samarium Discovery, Naming, and Isolation

Samarium was discovered in 1879 by the French chemist Paul Émile Lecoq de Boisbaudran. He identified the new element in the mineral samarskite, named after a Russian mine official, Colonel Vasili Samarsky-Bykhovets. Samarium was isolated in its pure form by the French chemist Eugène-Anatole Demarçay in 1901, through the process of fractional crystallization.

The modern symbol for samarium is Sm, but the symbol Sa was common until the 1920s.

Appearance and Properties

Samarium is a hard, silvery-white metal that tarnishes in air, giving it a dull golden appearance. It oxidizes and develops a gray-yellow color even when stored under mineral oil. However, the pure silver color remains intact under argon gas. The pure metal spontaneously ignites at 150 °C (302 °F).It has a relatively high melting point and is moderately stable at room temperature. It exhibits the high density and malleability that are characteristic of members of the lanthanide group. It has a high affinity for oxygen and a tendency to form trivalent ions. Samarium is paramagnetic at room temperature, but becomes antiferromagnetic upon cooling down to 14.1 K.

Crystal Structure

The element displays a rhombohedral α form under ordinary conditions that transitions to a hexagonal close-packed (hcp) form upon heating. Further heating to 922 °C (1,692 °F) transitions the structure into the body-centered cubic (bcc) form. Exposure to further heat and pressure produces a double-hexagonally close-packed (dhcp) and tetragonal phase.

Natural and Radioactive Isotopes

Natural samarium consists of seven isotopes. Of these, five are stable: 144Sm, 149Sm, 150Sm, 152Sm, and 154Sm. Its natural radioisotopes are 147Sm (half-life of 1.06 x 1011 years) and 148Sm (half-life 7 x 1015 years). There are also numerous synthetic radioisotopes.

Abundance and Sources

Samarium does not occur free in nature. It occurs in minerals that include monazite, bastnäsite, cerite, gadolinite, and samarskite. Sources of these minerals are China, the United States, Brazil, Australia, India, and Sri Lanka. It is the 40th most abundant element in the Earth’s crust, making it slightly more common than tin. It is a primordial element that was present before the formation of the solar system.

Purification

The purification of samarium involves complex processes like solvent extraction and ion exchange, which are standard in the processing of rare earth elements.

Uses of Samarium

The primary use of samarium is in samarium-cobalt magnets. However, it has several other important applications.

  • Alloys: Samarium is a component of permanent magnets that are second in strength to neodymium magnets yet withstand much higher temperatures.
  • Catalysts: The element acts as a catalyst in chemical reactions.
  • Nuclear Reactors: Samarium has applications in the nuclear industry due to its neutron absorption properties.
  • Medicine: Samarium isotopes are useful in cancer treatment as painkiller and for killing cancer cells.
  • Lasers: The element finds use in the production of x-ray lasers.
Electron Levels of a Samarium Atom

Oxidation States and Main State

Samarium primarily exhibits the +3 oxidation state, but it can also exist in 0, +1, and +2 states in some compounds.

Biological Role, Health Effects, and Toxicity

Samarium has no known biological role and is not present in appreciable amounts in plants. It displays low absorption and toxicity. Of the absorbed samarium, around 45% deposits on bones, 45% goes to the liver, and 10% is excreted. Samarium salts stimulate metabolism.

Samarium Facts for Scientists

PropertyDetail
NameSamarium
SymbolSm
Atomic Number62
Atomic Weight150.36
GroupLanthanide
Period6
Blockf-block
Electron Configuration[Xe] 4f6 6s2
Electrons Per Shell2, 8, 18, 24, 8, 2
State of Matter at Room T.Solid
Melting Point1072 °C
Boiling Point1900 °C
Density7.52 g/cm^3
Heat of Fusion8.62 kJ/mol
Heat of Vaporization192 kJ/mol
Molar Heat Capacity29.54 J/(mol·K)
Oxidation States0, +1, +2, +3
ElectronegativityPauling scale: 1.17
Ionization Energies1st: 544.5 kJ/mol
Atomic Radiusempirical: 180 pm
Covalent Radius198±8 pm
Crystal StructureRhombohedral
Thermal Conductivity13.3 W/(m·K)
Electrical Resistivity~0.94 µΩ·m (at 25 °C)
Young’s Modulus49.7 GPa
Shear Modulus19.5 GPa
Bulk Modulus37.8 GPa
Mohs Hardness~5
Magnetic OrderingParamagnetic

Interesting Samarium Facts

  1. Color-Changing Properties: Samarium exhibits different colors depending on its oxidation state. For example, Sm(III) compounds are typically pale yellow or green, while Sm(II) ions are blood-red in water.
  2. Space Age Material: Samarium is a key element in samarium-cobalt magnets, which are essential in the construction of satellites and spacecraft due to their ability to withstand extreme temperatures and radiation.
  3. Dating the Earth’s History: Samarium-neodymium dating is a form of radiometric dating used by geologists for determining the age of rocks and meteorites.
  4. Unique Spectral Lines: Samarium has an absorption spectrum that is unusually rich and complex, making it useful in calibrating spectrophotometers.
  5. Use in Cancer Therapy: Samarium-153 lexidronam is a radioactive compound that offers pain relief for cancer patients.
  6. Role in Quantum Computing: Research suggests that certain samarium compounds have potential applications in quantum computing due to their unique magnetic and electrical properties.
  7. Presence in the Stars: Samarium spectral lines occur in the spectra of certain stars, helping astronomers study the chemical composition and age of these celestial bodies.
  8. Impact on Electrical Conductivity: Samarium increases the electrical conductivity of certain materials when added in small quantities.
  9. Historical Anomaly in Naming: Samarium is one of the few elements named after a person who was not a scientist (Colonel Vasili Samarsky-Bykhovets). It was the first element that was named for a person, although indirectly.
  10. Contribution to Glass and Ceramics: Samarium oxide helps glass and ceramics absorb infrared radiation. It protects against UV radiation and acts as a decolorizer to counteract the greenish tint caused by iron impurities in glass.

References

  • Emsley, John (2001). “Samarium”. Nature’s Building Blocks: An A–Z Guide to the Elements. Oxford, England, UK: Oxford University Press. pp. 371–374. ISBN 0-19-850340-7.
  • Finlay, I. G.; Mason, M. D.; Shelley, M. (2005). “Radioisotopes for the palliation of metastatic bone cancer: a systematic review”. The Lancet Oncology. 6 (6): 392–400. doi:10.1016/S1470-2045(05)70206-0
  • Hammond, C. R. (2004). “The Elements”. Handbook of Chemistry and Physics (81st ed.). Boca Raton New York Washington: CRC press. ISBN 978-0-8493-0481-1.
  • Lide, D. R., ed. (2005). CRC Handbook of Chemistry and Physics (86th ed.). Boca Raton (FL): CRC Press. ISBN 0-8493-0486-5.
  • Weast, Robert (1983). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. ISBN 978-0-8493-0464-4.