Samarium (Sm)
lanthanideSolid
Peso atomico standard
150,36 uConfigurazione elettronica
[Xe] 6s2 4f6Punto di fusione
1073,85 °CPunto di ebollizione
1793,85 °CDensità
7520 kg/m³Stati di ossidazione
0, +1, +2, +3Elettronegatività (Pauling)
1,17Energia di ionizzazione (1ª)
5,643722 eVAnno della scoperta
1878Raggio atomico
185 pmDettagli
Samarium is a lanthanide metal with atomic number 62. It is a typical rare-earth element in its trivalent chemistry, but it is also notable for accessible divalent compounds and for the strong neutron-absorbing isotope ¹⁴⁹Sm. The element occurs with other light rare earths in minerals such as monazite and bastnäsite. Its technological importance is concentrated in permanent magnets, neutron control, phosphors, and specialized chemical reducing agents.
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.
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.
Pure samarium is a silvery, moderately hard metal that tarnishes in air as oxide forms on the surface. It has the close-packed metallic character typical of lanthanides and is normally handled as ingots, pieces, powder, or alloy feedstock under conditions that limit oxidation.
The largest distinctive use of samarium is in samarium-cobalt permanent magnets, mainly SmCo₅ and Sm₂Co₁₇, which retain magnetization at higher temperatures and resist corrosion better than many neodymium magnets. ¹⁴⁹Sm is an effective neutron absorber and samarium compounds are used in control materials and reactor physics applications. Samarium-doped materials serve in some phosphors, lasers, and infrared-absorbing glasses. Samarium(II) iodide, SmI₂, is an important one-electron reducing reagent in organic synthesis.
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.
Isotopes in Earth/Planetary Science
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] R. M. Canup, E. Asphaug. Nature412, 708 (2001).. 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] A. Brandon. Nature450, 1169 (2007)., along with measurements of isotopes of hafnium, tungsten, and neodymium [438] K. Righter, C. K. Shearer. Geochim. Cosmochim. Acta67, 2497 (2003)., 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] J. Edmunson, L. E. Borg. “The formation age of KREEP based on the 147Sm-143Nd geochemistry of KREEP-rich rocks: duration of lunar magma ocean crystallization and similarity to early mars”, in Workshop on Early Planetary Differentiation..
Isotopes in Geochronology
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] T. Iizuka, O. Nebel, M. McCulloch. Early Crustal Evolution Deduced from a Combined U-Pb and Sm-Nd Isotopic Study of Mt. Narryer and Jack Hills Monazites, The Australian National University (2014), Feb. 28; http://rses.anu.edu.au/highlights/view.php?article=191., [441] K. Rankenburg, A. D. Brandon, C. R. Neal. Science312 1369 (2006)., [442] F. F. Hu, H. R. Fan, S. Liu, K. F. Yang, F. Chen. Resour. Geol.59, 407 (2009)..
Isotopes in Medicine
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] International Atomic Energy Agency. Optimization of Production and Quality Control of Therapeutic Radionuclides and Radiopharmaceuticals, IAEA-TECDOC-1114, IAEA VIENNA (1999)., [444] C. L. Maini, S. Bergomi, L. Romano, R. Sciuto. Eur. J. Nucl. Med. Mol. Imaging31, S171 (2004)., [445] N. Pandit-Taskar, M. Batraki, C. R. Divgi. J. Nucl. Med.45, 1358 (2004)..
Isotopes Used as a Source of Radioactive Isotope(s)
147Sm bombarded with 40Ca produces the radioisotope 182Pb [446] K. S. Toth, D. M. Moltz, J. M. Nitschke, P. A. Wilmarth, J. D. Robertson. AIP Conference Proc.283, 347 (1991)..
Samarium most commonly forms Sm³⁺ salts and oxides. Samarium(III) oxide, Sm₂O₃, is a stable sesquioxide used as a starting material for many other compounds. Halides such as samarium(III) chloride, SmCl₃, and samarium(III) fluoride, SmF₃, are typical ionic rare-earth salts. The Sm²⁺ state is less common but chemically important; samarium(II) iodide, SmI₂, is a mild, selective reductant, and samarium(II) sulfide, SmS, shows pressure-sensitive electronic behavior. Mixed-valence chemistry is known in some solids.
See more information at the Samarium compound page.
Compact samarium metal has low acute toxicity, but finely divided metal can burn and should be kept from ignition sources. Dusts and soluble samarium salts may irritate tissues and should not be inhaled or ingested. Natural samarium is weakly radioactive because of long-lived isotopes, especially ¹⁴⁷Sm and ¹⁴⁸Sm, but its specific activity is low. Reactor-produced or isotope-enriched materials can present additional radiation hazards depending on isotopic composition.
Little is known of the toxicity of samarium; therefore, it should be handled carefully.
Samarium is dispersed in the crust as a minor component of rare-earth minerals rather than as native metal. In soils and waters it is generally present as Sm³⁺ associated with phosphates, carbonates, oxides, and organic ligands. It is not known to have an essential biological role. Mining and processing can mobilize samarium together with other rare earths and, in monazite deposits, with thorium and uranium by-products.
Samarium is produced as part of rare-earth separation rather than from samarium-specific ores. Concentrates from monazite and bastnäsite are chemically processed, and individual rare earths are separated by solvent extraction or ion-exchange methods before conversion to oxides, metals, or alloys. Demand is much smaller than for cerium, lanthanum, or neodymium, but it is strategically important where high-temperature Sm-Co magnets are required. Recycling is limited compared with primary production, partly because samarium is often present in durable, specialized magnet assemblies.
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.
Samarium is a heavy element made mainly by neutron-capture processes in earlier generations of stars. Its stable and long-lived isotopes reflect contributions from both slow and rapid neutron-capture nucleosynthesis. In planetary materials it is lithophile and follows other rare earths into refractory minerals, making samarium-neodymium isotope systematics useful in geochemistry and cosmochemistry.
- Samarium was named from the mineral samarskite, which was itself named after Vasili Samarsky-Bykhovets.
- ¹⁴⁷Sm decays very slowly to ¹⁴³Nd and is used in Sm-Nd radiometric dating.
- ¹⁴⁹Sm has one of the largest thermal-neutron capture cross sections among naturally occurring nuclides.
- Samarium-cobalt magnets preceded modern neodymium-iron-boron magnets in many high-performance applications.
- SmS can change from a black semiconducting phase toward a golden metallic state under pressure.
Immagini
Proprietà
Fisiche
- Raggio atomico (empirico)
- 185 pm Confronta Raggio atomico (empirico) di tutti gli elementi →
- Raggio covalente
- 198 pm Confronta Raggio covalente di tutti gli elementi →
- Raggio di van der Waals
- 229 pm Confronta Raggio di van der Waals di tutti gli elementi →
- Densità
- 7520 kg/m³ Confronta Densità di tutti gli elementi →
- Volume molare
- 0,0199 L/mol
- Fase in condizioni STP
- Solido Confronta Fase in condizioni STP di tutti gli elementi →
- Punto di fusione
- 1073,85 °C Confronta Punto di fusione di tutti gli elementi →
- Punto di ebollizione
- 1793,85 °C Confronta Punto di ebollizione di tutti gli elementi →
- Capacità termica specifica
- 0,197 J/(g·K) Confronta Capacità termica specifica di tutti gli elementi →
- Capacità termica molare
- 29,54 J/(mol·K) Confronta Capacità termica molare di tutti gli elementi →
- Struttura cristallina
- Romboedrica Confronta Struttura cristallina di tutti gli elementi →
Chimiche
- Elettronegatività (Pauling)
- 1,17 Confronta Elettronegatività (Pauling) di tutti gli elementi →
- Affinità elettronica
- 0,156 eV
- Energia di ionizzazione (1ª)
- 5,643722 eV Confronta Energia di ionizzazione (1ª) di tutti gli elementi →
- Energia di ionizzazione (2ª)
- 11,078038 eV Confronta Energia di ionizzazione (2ª) di tutti gli elementi →
- Energia di ionizzazione (3ª)
- 23,550081 eV Confronta Energia di ionizzazione (3ª) di tutti gli elementi →
- Energia di ionizzazione (4ª)
- 41,640143 eV Confronta Energia di ionizzazione (4ª) di tutti gli elementi →
- Energia di ionizzazione (5ª)
- 62,700216 eV Confronta Energia di ionizzazione (5ª) di tutti gli elementi →
- Stati di ossidazione
- 0, +1, +2, +3 Confronta Stati di ossidazione di tutti gli elementi →
- Elettroni di valenza
- 3 Confronta Elettroni di valenza di tutti gli elementi →
- Configurazione elettronica
- [Xe] 6s2 4f6
Termodinamiche
- Calore di fusione
- 0,08934031 eV Confronta Calore di fusione di tutti gli elementi →
- Calore di vaporizzazione
- 1,71011 eV Confronta Calore di vaporizzazione di tutti gli elementi →
- Calore di sublimazione
- 2,145411 eV
- Calore di atomizzazione
- 2,145411 eV
- Entalpia di atomizzazione
- 2,142302 eV
Nucleari
- Protoni
- 62 Confronta Protoni di tutti gli elementi →
- Neutroni
- 90 Confronta Neutroni di tutti gli elementi →
- Isotopi noti
- 41 Confronta Isotopi noti di tutti gli elementi →
- Isotopi stabili
- 3 Confronta Isotopi stabili di tutti gli elementi →
- Isotopo più stabile
- Sm-152
- Anno della scoperta
- 1878
Abbondanza
- Abbondanza (crosta terrestre)
- 7,05 mg/kg Confronta Abbondanza (crosta terrestre) di tutti gli elementi →
- Abbondanza (oceano)
- 4,5 × 10−7 mg/L Confronta Abbondanza (oceano) di tutti gli elementi →
Struttura cristallina
- Costante reticolare a
- 900 pm
Struttura elettronica
- Elettroni per guscio
- 2, 8, 18, 24, 8, 2 Confronta Elettroni per guscio di tutti gli elementi →
Identificativi
- Numero CAS
- 7440-19-9 Confronta Numero CAS di tutti gli elementi →
- Simbolo di termine
- 7F0
- InChI
- InChI=1S/Sm
- Chiave InChI
- KZUNJOHGWZRPMI-UHFFFAOYSA-N
Configurazione elettronica Misurato
Sm: 4f⁶ 6s²[Xe] 4f⁶ 6s²1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 4f⁶ 6s²Modello atomico
Gli isotopi modificano il numero di neutroni, la massa e la stabilità — non la configurazione elettronica di un atomo neutro.
Modello atomico schematico, non in scala.
Impronta atomica
Spettro di emissione / assorbimento
Distribuzione isotopica
| Numero di massa | Massa atomica (u) | Abbondanza naturale | Emivita |
|---|---|---|---|
| 144 Stabile | 143,9120065 ± 0,0000021 | 3,0700% | Stabile |
| 150 Stabile | 149,9172829 ± 0,0000018 | 7,3800% | Stabile |
| 152 Stabile | 151,9197397 ± 0,0000018 | 26,7500% | Stabile |
Fase / Stato
Motivo: 1048,8 °C sotto il punto di fusione (1073,85 °C)
Schema non in scala
Punti di transizione di fase
Energie di transizione
Energia necessaria per fondere 1 mol al punto di fusione
Energia necessaria per vaporizzare 1 mol al punto di ebollizione
Energia necessaria per sublimare 1 mol al punto di sublimazione
Densità
In condizioni standard
In condizioni standard
Spettri atomici
Sono visualizzati 10 di 62. Ordinamento per carica ionica crescente.
Righe disponibili ?
| Ione | Carica | Righe totali | Probabilità di transizione | Designazioni dei livelli |
|---|---|---|---|---|
| Sm I | 0 | 162 | 7 | 11 |
| Sm II | +1 | 635 | 7 | 14 |
Livelli disponibili ?
| Ione | Carica | Livelli |
|---|---|---|
| Sm I | 0 | 501 |
| Sm II | +1 | 377 |
| Sm III | +2 | 58 |
| Sm IV | +3 | 24 |
| Sm V | +4 | 2 |
| Sm VI | +5 | 2 |
| Sm VII | +6 | 2 |
| Sm VIII | +7 | 2 |
| Sm IX | +8 | 2 |
| Sm X | +9 | 2 |
Dati sulla struttura cristallina non disponibili
Struttura cristallina: rhombohedral
Raggi ionici
| Carica | Coordinazione | Spin | Raggio |
|---|---|---|---|
| +2 | 7 | N/D | 122 pm |
| +2 | 8 | N/D | 127 pm |
| +2 | 9 | N/D | 132 pm |
| +3 | 6 | N/D | 95.8 pm |
| +3 | 7 | N/D | 102 pm |
| +3 | 8 | N/D | 107.89999999999999 pm |
| +3 | 9 | N/D | 113.19999999999999 pm |
| +3 | 12 | N/D | 124 pm |
Composti
Isotopi (3)
Twenty one isotopes of samarium exist. Natural samarium is a mixture of several isotopes, three of which are unstable with long half-lives.
| Numero di massa | Massa atomica (u) | Abbondanza naturale | Emivita | Modalità di decadimento | |
|---|---|---|---|---|---|
| 144 Stabile | 143,9120065 ± 0,0000021 | 3,0700% ± 0,0700% | Stabile | stable | |
| 150 Stabile | 149,9172829 ± 0,0000018 | 7,3800% ± 0,0100% | Stabile | stable | |
| 152 Stabile | 151,9197397 ± 0,0000018 | 26,7500% ± 0,1600% | Stabile | stable |
Proprietà estese
Raggi covalenti (dati estesi)
- Raggio covalente (Pyykkö)
- 172 pm
- Raggio covalente (Pyykkö, legame doppio)
- 134 pm
Raggi di van der Waals
- Alvarez
- 290 pm
- UFF
- 352 pm
- MM3
- 271 pm
Raggi atomici e metallici
- Raggio atomico (Rahm)
- 280 pm
Scale di numerazione
- Mendeleev
- 23
- Pettifor
- 28
- Glawe
- 27
Scale di elettronegatività
- Ghosh
- 0
- Miedema
- 3
- Gunnarsson–Lundqvist
- 6
- Robles–Bartolotti
- 5
Polarizzabilità e dispersione
- Polarizzabilità dipolare
- 192 a.u.
- Polarizzabilità dipolare (inc.)
- 20 a.u.
- C₆ (Gould–Bučko)
- 3130 Ha·Bohr6
Parametri di Miedema
- Volume molare di Miedema
- 20,01 cm3/mol
- Densità elettronica di Miedema
- 2
Rischio di approvvigionamento ed economia
- Concentrazione della produzione
- 97
- Rischio relativo di approvvigionamento
- 10
- Distribuzione delle riserve
- 50
- Stabilità politica (principale produttore)
- 24
- Stabilità politica (principale detentore di riserve)
- 24
Transizioni di fase e allotropi
| Punto di fusione | 1345,15 K |
| Punto di ebollizione | 2067,15 K |
Categorie degli stati di ossidazione
Dati di riferimento avanzati
Costanti di schermaggio (13)
| n | Orbitale | σ |
|---|---|---|
| 1 | s | 1,2217 |
| 2 | p | 4,269 |
| 2 | s | 16,2652 |
| 3 | d | 13,7711 |
| 3 | p | 19,5815 |
| 3 | s | 19,9736 |
| 4 | d | 33,7604 |
| 4 | f | 38,4684 |
| 4 | p | 30,912 |
| 4 | s | 29,7076 |
Dettaglio dei raggi cristallini (8)
| Carica | CN | Spin | rcrystal (pm) | Origine |
|---|---|---|---|---|
| 2 | VII | 136 | ||
| 2 | VIII | 141 | ||
| 2 | IX | 146 | ||
| 3 | VI | 109,8 | from r^3 vs V plots, | |
| 3 | VII | 116 | estimated, | |
| 3 | VIII | 121,9 | from r^3 vs V plots, | |
| 3 | IX | 127,2 | from r^3 vs V plots, | |
| 3 | XII | 138 | calculated, |
Modalità di decadimento degli isotopi (52)
| Isotopo | Modalità | Intensità |
|---|---|---|
| 128 | B+ | — |
| 128 | B+p | — |
| 129 | B+ | 100% |
| 129 | B+p | — |
| 130 | B+ | — |
| 131 | B+ | 100% |
| 131 | B+p | — |
| 132 | B+ | 100% |
| 132 | B+p | — |
| 133 | B+ | 100% |
Fattori di diffusione dei raggi X (508)
| Energia (eV) | f₁ | f₂ |
|---|---|---|
| 10 | — | 0,18764 |
| 10,1617 | — | 0,19534 |
| 10,3261 | — | 0,20334 |
| 10,4931 | — | 0,21168 |
| 10,6628 | — | 0,22036 |
| 10,8353 | — | 0,22939 |
| 11,0106 | — | 0,2388 |
| 11,1886 | — | 0,24859 |
| 11,3696 | — | 0,25878 |
| 11,5535 | — | 0,26939 |
Dati aggiuntivi
Estimated Crustal Abundance
The estimated element abundance in the earth's crust.
7.05 milligrams per kilogram
Riferimenti (1)
- [5] Samarium https://education.jlab.org/itselemental/ele062.html
Estimated Oceanic Abundance
The estimated element abundance in the earth's oceans.
4.5×10-7 milligrams per liter
Riferimenti (1)
- [5] Samarium https://education.jlab.org/itselemental/ele062.html
Sources
Sources of this element.
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.
Riferimenti (1)
- [6] Samarium https://periodic.lanl.gov/62.shtml
Riferimenti
(9)
Data deposited in or computed by PubChem
The half-life and atomic mass data was provided by the Atomic Mass Data Center at the International Atomic Energy Agency.
Element data are cited from the Atomic weights of the elements (an IUPAC Technical Report). The IUPAC periodic table of elements can be found at https://iupac.org/what-we-do/periodic-table-of-elements/. Additional information can be found within IUPAC publication doi:10.1515/pac-2015-0703 Copyright © 2020 International Union of Pure and Applied Chemistry.
The information are cited from Pure Appl. Chem. 2018; 90(12): 1833-2092, https://doi.org/10.1515/pac-2015-0703.
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The periodic table at the LANL (Los Alamos National Laboratory) contains basic element information together with the history, source, properties, use, handling and more. The provenance data may be found from the link under the source name.
The periodic table contains NIST's critically-evaluated data on atomic properties of the elements. The provenance data that include data for atomic spectroscopy, X-ray and gamma ray, radiation dosimetry, nuclear physics, and condensed matter physics may be found from the link under the source name. Ref: https://www.nist.gov/pml/atomic-spectra-database
This section provides all form of data related to element Samarium.
The element property data was retrieved from publications.