| Atomic Mass | 150.36 |
|---|---|
| Electron Configuration | [Xe]6s24f6 |
| Oxidation States | +3, +2 |
| Year Discovered | 1879 |
| Atomic Mass | 150.36 |
|---|---|
| Electron Configuration | [Xe]6s24f6 |
| Oxidation States | +3, +2 |
| Year Discovered | 1879 |
| Element Name | Samarium |
|---|---|
| Element Symbol | Sm |
| InChI | InChI=1S/Sm |
| InChIKey | KZUNJOHGWZRPMI-UHFFFAOYSA-N |
| Atomic Weight |
150.36(2) 150.36 150.4 150.36(2) |
|---|---|
| Electron Configuration |
[Xe]6s24f6 |
| Atomic Radius |
Van der Waals Atomic Radius : 229 pm (Van der Waals) Empirical Atomic Radius : 185pm (Empirical) Covalent Atomic Radius : 198(8) pm (Covalent) |
| Oxidation States |
+3, +2 4, 3, 2, 1 (a mildly basic oxide) |
| Ground Level |
7F0 |
| Ionization Energy |
5.644 eV 5.643722 ± 0.000021 eV |
| Electronegativity |
Pauling Scale Electronegativity : 1.17(Pauling Scale) |
| Atomic Spectra |
Lines Holdings Levels Holdings |
| Physical Description |
Solid |
| Element Classification |
Metal |
| Element Period Number |
6 |
| Element Group Number |
- Lanthanide |
| Density |
7.52 grams per cubic centimeter |
| Melting Point |
1347 K (1074°C or 1965°F) 1072°C |
| Boiling Point |
2067 K (1794°C or 3261°F) 1900°C |
| Estimated Crustal Abundance |
7.05 milligrams per kilogram |
| Estimated Oceanic Abundance |
4.5×10-7 milligrams per liter |
The name derives from the mineral samarskite, in which it was found and that had been named for Colonel Samarski, a Russian mine official. Samarium was originally discovered in 1878 by the Swiss chemist Marc Delafontaine, who called it decipium. It was also discovered by the French chemist Paul-Emile Lecoq de Boisbaudran in 1879. In 1881, Delafontaine determined that his decipium could be resolved into two elements, one of which was identical to Boisbaudran's samarium. In 1901, the French chemist Eugène-Anatole Demarçay showed that this samarium earth also contained europium.
Samarium was observed spectroscopically by Jean Charles Galissard de Marignac, a Swiss chemist, in a material known as dydimia in 1853. Paul-Émile Lecoq de Boisbaudran, a French chemist, was the first to isolate samarium from the mineral samarskite ((Y, Ce, U, Fe)3(Nb, Ta, Ti)5O16) in 1879. Today, samarium is primarily obtained through an ion exchange process from monazite sand ((Ce, La, Th, Nd, Y)PO4), a material rich in rare earth elements that can contain as much as 2.8% samarium.
Discovered spectroscopically by its sharp absorption lines in 1879 by Lecoq de Boisbaudran in the mineral samarskite, named in honor of a Russian mine official, Col. Samarski.
| Year | Atomic Weight (uncertainty) [u] | Reference |
|---|---|---|
| 2005 | 150.36(2) | https://doi.org/10.1351/pac200678112051 |
| 1979 | 150.36(3) | https://doi.org/10.1351/pac198052102349 |
| 1969 | 150.4(1) | https://doi.org/10.1351/pac197021010091 |
| 1955 | 150.35 | https://doi.org/10.1021/ja01595a001 |
| 1925 | 150.43 | https://doi.org/10.1039/CT9252700913 |
| 1909 | 150.4 | https://doi.org/10.1021/ja01931a001 |
| 1905 | 150.3 | https://doi.org/10.1021/ja01979a001 |
| 1902 | 150 | https://doi.org/10.1007/BF01370337 |
Samarium has a bright silver luster and is reasonably stable in air. Three crystal modifications of the metal exist, with transformations at 734 and 922°C. The metal ignites in air at about 150°C. The sulfide has excellent high-temperature stability and good thermoelectric efficiencies up to 1100°C.
Samarium is one of the rare earth elements used to make carbon arc lights which are used in the motion picture industry for studio lighting and projector lights. Samarium also makes up about 1% of Misch metal, a material that is used to make flints for lighters.
Samarium forms a compound with cobalt (SmCo5) which is a powerful permanent magnet with the highest resistance to demagnetization of any material known. Samarium oxide (Sm2O3) is added to glass to absorb infrared radiation and acts as a catalyst for the dehydration and dehydrogenation of ethanol (C2H6O).
Samarium, along with other rare earths, is used for carbon-arc lighting for the motion picture industry. SmCo5 has been used in making a new permanent magnet material with the highest resistance to demagnetization of any known material. It is said to have an intrinsic coercive force as high as 2200 kA/m. Samarium oxide has been used in optical glass to absorb the infrared. Samarium is used to dope calcium fluoride crystal for use in optical lasers or lasers. Compounds of the metal act as sensitizers for phosphors excited in the infrared; the oxide exhibits catalytic properties in the dehydration and dehydrogenation of ethyl alcohol. It is used in infrared absorbing glass and as a neutron absorber in nuclear reactors.
Samarium is found along with other members of the rare-earth elements in many minerals, including monazite and bastnasite, which are commercial sources. It occurs in monazite to the extent of 2.8%. While misch metal containing about 1% of samarium metal, has long been used, samarium has not been isolated in relatively pure form until recently. Ion-exchange and solvent extraction techniques have recently simplified separation of the rare earths from one another; more recently, electrochemical deposition, using an electrolytic solution of lithium citrate and a mercury electrode, is said to be a simple, fast, and highly specific way to separate the rare earths. Samarium metal can be produced by reducing the oxide with lanthanum.
See more information at the Samarium compound page.
| CID | Name | Formula | SMILES | Molecular Weight |
|---|---|---|---|---|
| 23951 | samarium | Sm | [Sm] | 150.4 |
| 114941 | samarium-153 | Sm | [153Sm] | 152.92210 |
| 119249 | samarium(3+) | Sm+3 | [Sm+3] | 150.4 |
| 177480 | samarium-154 | Sm | [154Sm] | 153.92222 |
| 177554 | samarium-145 | Sm | [145Sm] | 144.91342 |
| 9877421 | samarium-152 | Sm | [152Sm] | 151.91974 |
| 25087174 | samarium-147 | Sm | [147Sm] | 146.91490 |
| 44154635 | samarium-146 | Sm | [146Sm] | 145.91305 |
| 114939 | samarium-151 | Sm | [151Sm] | 150.91994 |
| 177498 | samarium-150 | Sm | [150Sm] | 149.91728 |
| 177673 | samarium-156 | Sm | [156Sm] | 155.92554 |
| 10197772 | samarium-149 | Sm | [149Sm] | 148.91719 |
| 25086834 | samarium-144 | Sm | [144Sm] | 143.91201 |
| 167086 | samarium-155 | Sm | [155Sm] | 154.92465 |
| 177495 | samarium-141 | Sm | [141Sm] | 140.91848 |
| 177629 | samarium-142 | Sm | [142Sm] | 141.91521 |
| 90478796 | samarium-152(3+) | Sm+3 | [152Sm+3] | 151.91974 |
| 90479421 | samarium-153(3+) | Sm+3 | [153Sm+3] | 152.92210 |
| 25086833 | samarium-148 | Sm | [148Sm] | 147.91483 |
| 10103390 | samarium-157 | Sm | [157Sm] | 156.92842 |
Little is known of the toxicity of samarium; therefore, it should be handled carefully.
| Stable Isotope Count | 5 |
|---|---|
| Summary | Twenty one isotopes of samarium exist. Natural samarium is a mixture of several isotopes, three of which are unstable with long half-lives. |
One possible origin for the Moon is from debris ejected by an indirect giant impact of Earth by an astronomical body the size of Mars when the Earth was forming [436]. The kinetic energy liberated is thought to have melted a large part of the Moon forming a lunar magma ocean. Samarium isotope measurement results [437], along with measurements of isotopes of hafnium, tungsten, and neodymium[438], suggest that lunar magma formed about 70×106 years after the Solar System formed and had crystallized by about 215×106 years after formation. 147Sm (with a half-life of 1.06×1011 years) is used to study the formation of potassium, rare earth elements, and phosphorus-rich rocks [439].
147Sm is used for determining formation ages of igneous and metamorphic rocks via analysis of the minerals which compose them, such as those shown in Fig. IUPAC.62.1 [440], [441], [442].
![Fig. IUPAC.62.1: Cross plot of n(¹⁴³Nd)/n(¹⁴⁴Nd) isotope-amount ratio and n(¹⁴⁷Sm)/n(¹⁴⁴Nd) amount ratio of carbonate and fluorocarbonates at the Bayan Obo rare-earth-element-niobium-iron deposit in Inner Mongolia, China (modified from [442]). ¹⁴³Nd is produced by decay of ¹⁴⁷Sm. Rock containing higher amounts of ¹⁴⁷Sm at time of mineralization will over time produce higher amounts of ¹⁴³Nd (e.g. fluorite samples). Alternatively, rocks containing lower amounts of ¹⁴⁷Sm at time of mineralization will over time produce lower amounts of ¹⁴³Nd (e.g. huanghoite samples). Samples from an older mineralization event will have proportionally more ¹⁴³Nd because of the longer accumulation time for ¹⁴³Nd; thus, the slope of the line through the samples above correlates to the time since mineralization (formation), and such a line is called an isochron.](https://pubchem.ncbi.nlm.nih.gov/images/iupac/j_pac-2015-0703_fig_086.jpg)
The radioisotope 153Sm (with a half-life of 1.9 days) is used in medicine to treat the severe pain associated with cancer that has spread to bones (Fig. IUPAC.62.2) [443], [444], [445].
![Fig. IUPAC.62.2: Targeting of bone metastases with ¹⁵³Sm-EDTMP in a prostate cancer patient. ANT indicates the anterior view of the patient; POST indicates the posterior view of the patient; arrow represents uptake in the pubic bone of the patient. (Image Source: Pandit-Taskar, Batraki, and Divgi, 2004) [445].](https://pubchem.ncbi.nlm.nih.gov/images/iupac/j_pac-2015-0703_fig_087.jpg)
147Sm bombarded with 40Ca produces the radioisotope 182Pb [446].
| Isotope | Atomic Mass (uncertainty) [u] | Abundance (uncertainty) | |
|---|---|---|---|
| 144Sm | 143.912 01(1) | 0.0308(4) | 0.0307(7) |
| 147Sm | 146.914 90(1) | 0.1500(14) | 0.1499(18) |
| 148Sm | 147.914 83(1) | 0.1125(9) | 0.1124(10) |
| 149Sm | 148.917 191(9) | 0.1382(10) | 0.1382(7) |
| 150Sm | 149.917 282(9) | 0.0737(9) | 0.0738(1) |
| 152Sm | 151.919 739(8) | 0.2674(9) | 0.2675(16) |
| 154Sm | 153.922 22(1) | 0.2274(14) | 0.2275(29) |
| Nuclide | Atomic Mass and Uncertainty [u] | Half Life and Uncertainty | Discovery Year | Decay Modes, Intensities and Uncertainties [%] |
|---|---|---|---|---|
| 128Sm | 127.957971 ± 0.000537 [Estimated] | 500 ms [Estimated] | β+ ?; β+p ? | |
| 129Sm | 128.954557 ± 0.000537 [Estimated] | 550 ms ± 100 | 1999 | β+=100%; β+p=? |
| 130Sm | 129.948792 ± 0.000429 [Estimated] | 1 s [Estimated] | 1999 | β+ ? |
| 131Sm | 130.946022 ± 0.000429 [Estimated] | 1.2 s ± 0.2 | 1986 | β+=100%; β+p=? |
| 132Sm | 131.940805 ± 0.000322 [Estimated] | 4.0 s ± 0.3 | 1989 | β+=100%; β+p ? |
| 133Sm | 132.938560 ± 0.00032 [Estimated] | 2.89 s ± 0.16 | 1977 | β+=100%; β+p=? |
| 133Smm | 132.938560 ± 0.00032 [Estimated] | 3.5 s ± 0.4 | 1993 | β+=?; IT ?; β+p ? |
| 134Sm | 133.934110 ± 0.00021 [Estimated] | 9.5 s ± 0.8 | 1977 | β+=100% |
| 135Sm | 134.932520000 ± 0.000166 | 10.3 s ± 0.5 | 1977 | β+=100%; β+p=0.02±0.1% |
| 136Sm | 135.928275553 ± 0.000013416 | 47 s ± 2 | 1982 | β+=100% |
| 136Smm | 135.928275553 ± 0.000013416 | 15 us ± 1 | 1994 | IT=100% |
| 137Sm | 136.927007959 ± 0.000030718 | 45 s ± 1 | 1986 | β+=100% |
| 137Smm | 136.927007959 ± 0.000030718 | 20 s [Estimated] | β+ ? | |
| 138Sm | 137.923243988 ± 0.000012686 | 3.1 m ± 0.2 | 1982 | β+=100% |
| 139Sm | 138.922296631 ± 0.000011684 | 2.57 m ± 0.10 | 1971 | β+=100% |
| 139Smm | 138.922296631 ± 0.000011684 | 10.7 s ± 0.6 | 1973 | IT=93.7±0.5%; β+=6.3±0.5% |
| 140Sm | 139.918994714 ± 0.000013416 | 14.82 m ± 0.12 | 1967 | β+=100% |
| 141Sm | 140.918481545 ± 0.000009162 | 10.2 m ± 0.2 | 1967 | β+=100% |
| 141Smm | 140.918481545 ± 0.000009162 | 22.6 m ± 0.2 | 1967 | β+=99.69±0.3%; IT=0.31±0.3% |
| 142Sm | 141.915209415 ± 0.000002002 | 72.49 m ± 0.05 | 1959 | β+=100%; e+<5% |
| 142Smm | 141.915209415 ± 0.000002002 | 170 ns ± 2 | 1975 | IT=100% |
| 142Smn | 141.915209415 ± 0.000002002 | 480 ns ± 60 | 1979 | IT=100% |
| 143Sm | 142.914634848 ± 0.000002951 | 8.75 m ± 0.06 | 1956 | β+=100%; e+=40.0±2%; ε=60.0±2% |
| 143Smm | 142.914634848 ± 0.000002951 | 66 s ± 2 | 1960 | IT≈100%; β+=0.24±0.5% |
| 143Smn | 142.914634848 ± 0.000002951 | 30 ms ± 3 | 1969 | IT=100% |
| 144Sm | 143.912006285 ± 0.000001566 | Stable | 1933 | IS=3.08±0.4%; 2β+ ? |
| 144Smm | 143.912006285 ± 0.000001566 | 880 ns ± 25 | 1972 | IT=100% |
| 145Sm | 144.913417157 ± 0.000001594 | 340 d ± 3 | 1947 | ε=100% |
| 145Smm | 144.913417157 ± 0.000001594 | 3.52 us ± 0.16 | 1993 | IT=100% |
| 146Sm | 145.913046835 ± 0.000003269 | 68 My ± 7 | 1953 | α=100% |
| 147Sm | 146.914904401 ± 0.000001354 | 106.6 Gy ± 0.5 | 1933 | IS=15.00±1.4%; α=100% |
| 148Sm | 147.914829233 ± 0.000001337 | 6.3 Py ± 1.3 | 1933 | IS=11.25±0.9%; α=100% |
| 149Sm | 148.917191211 ± 0.000001241 | Stable >2Py | 1933 | IS=13.82±1%; α ? |
| 150Sm | 149.917281993 ± 0.000001193 | Stable | 1934 | IS=7.37±0.9% |
| 151Sm | 150.919938859 ± 0.000001191 | 94.6 y ± 0.6 | 1947 | β-=100% |
| 151Smm | 150.919938859 ± 0.000001191 | 1.4 us ± 0.1 | 1973 | IT=100% |
| 152Sm | 151.919738646 ± 0.00000109 | Stable | 1933 | IS=26.74±0.9% |
| 153Sm | 152.922103576 ± 0.0000011 | 46.2846 h ± 0.0023 | 1938 | β-=100% |
| 153Smm | 152.922103576 ± 0.0000011 | 10.6 ms ± 0.3 | 1971 | IT=100% |
| 154Sm | 153.922215756 ± 0.0000014 | Stable >2.3Ey | 1933 | IS=22.74±1.4%; 2β- ? |
| 155Sm | 154.924646645 ± 0.000001429 | 22.18 m ± 0.06 | 1951 | β-=100% |
| 155Smm | 154.924646645 ± 0.000001429 | 2.8 us ± 0.5 | 2010 | IT=100% |
| 155Smn | 154.924646645 ± 0.000001429 | 1.00 us ± 0.08 | 2010 | IT=100% |
| 156Sm | 155.925538191 ± 0.000009148 | 9.4 h ± 0.2 | 1951 | β-=100% |
| 156Smm | 155.925538191 ± 0.000009148 | 185 ns ± 7 | 1974 | IT=100% |
| 157Sm | 156.928418598 ± 0.000004759 | 8.03 m ± 0.07 | 1973 | β-=100% |
| 158Sm | 157.929949262 ± 0.000005133 | 5.30 m ± 0.03 | 1970 | β-=100% |
| 159Sm | 158.933217130 ± 0.00000637 | 11.37 s ± 0.15 | 1986 | β-=100% |
| 159Smm | 158.933217130 ± 0.00000637 | 116 ns ± 8 | 2009 | IT=100% |
| 160Sm | 159.935337032 ± 0.0000021 | 9.6 s ± 0.3 | 1986 | β-=100% |
| 160Smm | 159.935337032 ± 0.0000021 | 120 ns ± 46 | 2009 | IT=100% |
| 160Smn | 159.935337032 ± 0.0000021 | 1.8 us ± 0.4 | 2016 | IT=100% |
| 161Sm | 160.939160062 ± 0.000007318 | 4.8 s ± 0.4 | 1998 | β-=100% |
| 161Smm | 160.939160062 ± 0.000007318 | 2.6 us ± 0.4 | 2017 | IT=100% |
| 162Sm | 161.941621687 ± 0.000003782 | 2.7 s ± 0.3 | 2005 | β-=100% |
| 162Smm | 161.941621687 ± 0.000003782 | 1.78 us ± 0.07 | 2017 | IT=100% |
| 163Sm | 162.945679085 ± 0.0000079 | 1.3 s ± 0.5 | 2012 | β-=100% |
| 164Sm | 163.948550061 ± 0.0000044 | 1.43 s ± 0.24 | 2012 | β-=100%; β-n ? |
| 164Smm | 163.948550061 ± 0.0000044 | 600 ns ± 140 | 2014 | IT=100% |
| 165Sm | 164.953290 ± 0.000429 [Estimated] | 980 ms ± 210 | 2012 | β-=100%; β-n ? |
| 166Sm | 165.956575 ± 0.000429 [Estimated] | 800 ms ± 630 | 2017 | β-=100% |
| 167Sm | 166.962072 ± 0.000537 [Estimated] | 190 ms >550ns [Estimated] | 2018 | β- ?; β-n ? |
| 168Sm | 167.966033 ± 0.000322 [Estimated] | 340 ms >550ns [Estimated] | 2018 | β- ?; β-n ? |
