Samarium was discovered in 1879. Samarium-cobalt magnets have permanent magnetization and are used in musical instruments.
History and Discovery
Samarium was identified in the second half of the nineteenth century. In 1879, Paul Emile Lecoq de Biosbaudran isolated samarium oxide and hydroxide from the mineral samarskite ((Y,Ce,U,Fe)3(Nb,Ta,Ti)5O)16. With the help of sharp optical absorption lines, he identified new element. The element was impure and contained europium. Then in 1901, Eugene- Anatole Demarcay obtained the element in purified form. Boisbaudran named the element samaria because of mineral samarskite. He transformed the name samaria into samarium after the name of Vassili Samarsky-Bykhovets, who granted access to study mineral samples. The symbol Sa was used till 1920 than Sm was suggested for samarium .
|Periodic Table Classification||Group n/a
|State at 20C||Solid|
|Electron Configuration||[Xe] 4f6 6s2|
|Electron Shell||2, 8, 18, 24, 8, 2
|Density||7.52 g.cm-3 at 20°C|
|Atomic Mass||150.36 g.mol -1|
|Electronegativity according to Pauling||1.17|
Samarium is as abundant as tin in the Earth crust. It is about 8 parts per million, and 40th most abundant element in the Earth crust. It is present in many rare earth element but mostly it is extracted from the mineral bastnasite, monazite, cerite, gadolinite and samarskite. It is also present in nuclear fission products. Samarium is mostly present in China, Brazil, India, Srilanka and Australia.
Samarium is a silvery white, bright and hard metal. It is one of the lanthanide and is a rare earth metal. Its hardness and density are like zinc. Samarium is paramagnetic (material is weakly attracted by external magnets). Upon cooling on 14.8K the metal transform to antiferromagnetic state (magnetic movement related to the spin of electrons). Samarium chemical symbol is Sm. Its atomic number is 62 and atomic weight is 150.36. The melting point of samarium is 1072OC and boiling point is 1900OC.
Samarium is slowly oxidized at room temperature. It spontaneously ignites at 150OC. It is oxidized and converted into a grayish-yellow powder of oxide-hydroxide mixture at the surface when stored under mineral oil. Its metallic appearance can be preserved by storing it under an inert gas like argon. It is electropositive in nature and react slowly with cold water and quite quickly with hot water to form hydroxide. Samarium readily dissolve in dilute sulfuric acid and form solution which contain the yellow to pale green Sm (lll) ions. It mostly exist in the oxidation state +2. Samarium form stable oxide Sm2O3 called sesquioxide, and also forms monoxide SmO. It reacts with all the halogens and forms trihalides .
Significance and Uses
- Samarium based magnets have high tendency for demagnetization.
- Its magnets are found in small motors, headphones, guitars and musical instruments.
- In the form of catalyst, it is used in the decomposition of plastics and dechlorination of pollutants.
- Samarium (ll) iodide is used as reducing agent and coupling agent in organic compound synthesis.
- Samarium-153 is used to kill cancer cells and in the treatment of lung cancer, prostate cancer, breast cancer and osteosarcoma.
- Samarium-149 is used to control rods of nuclear reactors.
- Samarium-doped calcium fluoride crystal is used as active medium in solid state laser.
- Samarium in the form of oxides is used for making special infrared adsorbing glass.
- It is also used in the cores of carbon arc-lamp electrodes.
- It is widely used in the dehydration and dehydrogenation of ethanol.
- Samarium with cobalt is used to make new permanent magnet material.
Samarium salts are mildly toxic in nature and it cause health hazards. Exposure to samarium causes eye and skin irritability. Its biological role is not clear. When ingested only 0.05% salts is absorbed in the blood stream and rest is excreted.
Isotopes of Samarium
Samarium is composed of four stable isotopes: 144Sm, 150Sm, 152Sm and 154Sm. It has three extremely long-lived radioisotopes: 147Sm (half-life: 1.06 x 1011 years), 148Sm (7 x 1015 years) and 149Sm (˃2 x 1015 years). 151Sm and 145 Sm have half -lives are 90 years and 340 days. All remaining radioisotopes have half-lives less than 2 days and less than 48 seconds. Samarium also has 5 nuclear isomers (metastable state of an atomic nucleus) in which the most stable is 141mSm (22.6 minutes), 143m1Sm (66 seconds) and 139mSm (10.7 seconds) .
. Hammond, C. R. “The Elements”. Handbook of Chemistry and Physics (81st ed.). CRC press. ISBN0-8493-0485-7.
. Chart of the nuclides, Brookhaven National Laboratory