Overview

Samarium is a metallic chemical element with the symbol Sm and atomic number 62. It is a member of the lanthanide, or rare-earth, series and appears as a silvery to gray metal that oxidizes on exposure to air. For basic reference see the periodic table and broader context at chemical element summaries.

Physical and chemical properties

In atoms of samarium there are 62 protons, which defines its position in the periodic system and its chemical behaviour; detailed atomic data and classification are available from standard references (atomic number and structure). Its electron configuration is commonly written as [Xe] 4f6 6s2. Samarium typically exhibits +3 oxidation state in compounds, while +2 compounds also occur. The metal reacts slowly with water and forms a stable oxide, Sm2O3, on exposure to air.

Occurrence and historical notes

Samarium does not occur free in nature; it is extracted from rare-earth minerals such as samarskite, monazite and bastnäsite. The element takes its name from the mineral samarskite, which in turn commemorates a Russian mining official. It was identified and isolated in the 19th century from those mineral sources and later characterized as part of the lanthanide group.

Applications and importance

Samarium has several specialized uses. It is most widely known for samarium–cobalt (SmCo) permanent magnets, prized in applications requiring high coercivity and thermal stability. Other uses include glass and ceramic additives, catalysts, and scientific research. Notable practical roles include:

  • High-performance magnets for motors, instruments, and aerospace.
  • Neutron-absorbing materials and control applications in nuclear technology.
  • Medical radiopharmaceuticals: certain radioactive isotopes are used for palliation of bone pain.
  • Geochronology: samarium–neodymium dating is an established method for determining geological ages (isotope applications).

Isotopes and safety

Natural samarium consists of a mix of stable and long-lived isotopes. Some isotopes have significant neutron capture properties and are relevant in reactor physics. Handling metallic samarium requires standard precautions for reactive rare-earth metals: avoid inhalation of dust, prevent contact with strong oxidizers, and store under suitable conditions. Chemical toxicity is generally low compared with heavy metals, but particulate and soluble forms should be managed to minimize exposure.