Samarium
Soft silvery metallic element, belongs to the lanthanoids. Seven natural isotopes, Sm-147 is the only radioisotope, and has a half-life of 2.5*10^11 years. Used for making special alloys needed in the production of nuclear reactors. Also used as a neutron absorber. Small quantities of samarium oxide is used in special optical glasses. The largest use of the element is its ferromagnetic alloy which produces permanent magnets that are five times stronger than magnets produced by any other material. Discovered by Francois Lecoq de Boisbaudran in 1879.
Gallery
Unknown authorUnknown author, CC BY 1.0 <https://creativecommons.org/licenses/by/1.0>, via Wikimedia Commons, source: https://images-of-elements.com/samarium.php
Physical Propertiesmass · density · phase · crystal
Atomic Mass
150.3600Da
Density
7.5200g/cm³
Phase (STP)
Solid
Melting Point
1345.2K
Boiling Point
2067.2K
Molar Heat
0.1970J/(mol·K)
Crystal Structure
RHL
Lattice Constant
9Å
Atomic Radiiatomic · covalent · van der Waals
Atomic (Empirical)
185.00pm
Covalent
172.00pm
Van der Waals
236.00pm
Electronic Propertieselectronegativity · ionization · affinity
Electron Configuration
[Xe] 4f6 6s2
Electron Shells
2, 8, 18, 24, 8, 2
Electronegativity
1.17Pauling
Electron Affinity
—
1st Ionization Energy
5.6kJ/mol
Oxidation States
+2, +3
Orbital DiagramAufbau · Hund's rule · Pauli exclusion
Full: 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6 4f6 6s2Short: [Xe] 4f6 6s2
Ionization Energies (62 known)
Emission Spectrumvisible range · characteristic spectral lines
Abundanceby mass
Log scale · ppm = parts per million by mass
Biological Role
No known biological role. Sm-153 used in bone cancer pain treatment.
Discovery
Discovered By
Paul Émile Lecoq de Boisbaudran
Named By
—
Year
1879
Nuclear Data
Known Isotopes
41
Stable Isotopes
5
Stable Mass Numbers
144, 149, 150, 152, 154
Natural isotopic abundance (IUPAC recommended values)
Isotopes of Sm41 known
| Nuclide | Z | N | Mass (AMU) | Half-life | Decay | Jπ | Abundance |
|---|---|---|---|---|---|---|---|
| 128Sm | 62 | 66 | 127.957971 | Unknown | β⁺, β⁺p | 0+ | — |
| 129Sm | 62 | 67 | 128.954557 | 550 ms | β⁺ (1%), β⁺p | 1/2+ | — |
| 130Sm | 62 | 68 | 129.948792 | Unknown | β⁺ | 0+ | — |
| 144Smstable | 62 | 82 | 143.912006 | Stable | 2β⁺ | 0+ | 308.0000% |
| 147Sm | 62 | 85 | 146.914904 | 107 Gy | α (1%) | 7/2- | 1500.0000% |
| 148Sm | 62 | 86 | 147.914829 | 6300000 Gy | α (1%) | 0+ | 1125.0000% |
| 149Smstable | 62 | 87 | 148.917191 | Stable | α | 7/2- | 1382.0000% |
| 150Smstable | 62 | 88 | 149.917282 | Stable | stable (1%) | 0+ | 737.0000% |
| 152Smstable | 62 | 90 | 151.919739 | Stable | stable (1%) | 0+ | 2674.0000% |
| 154Smstable | 62 | 92 | 153.922216 | Stable | 2β⁻ | 0+ | 2274.0000% |
| 166Sm | 62 | 104 | 165.956575 | 800 ms | β⁻ (1%) | 0+ | — |
| 167Sm | 62 | 105 | 166.962072 | Unknown | β⁻, β⁻n | 7/2- | — |
| 168Sm | 62 | 106 | 167.966033 | Unknown | β⁻, β⁻n | 0+ | — |