Samarium
Samarium is a rare-earth metal useful in magnetic alloys and neutron-absorbing materials.
Samarium helps magnets keep working at elevated temperatures.
Explore Samarium's atom- Atomic number
- 62
- Standard atomic weight
- 150.36(2)
- Family
- Lanthanide
- Period
- 6
- Group
- f-block
- Standard state
- Solid
In everyday life
Samarium-cobalt magnets are used where temperature resistance matters.
Something to remember
Samarium was named through a mineral, samarskite, rather than directly after a place.
Meet its electrons
[Xe] 6s2 4f6
Published neutral-atom ground-state configuration; excited atoms and ions can differ.
Electrons per shell: 2 · 8 · 18 · 24 · 8 · 2.
The playground shows an illustrative shell model. Real electrons are described by quantum orbitals, rather than tiny planets traveling along fixed paths.
A connection to explore
Samarium and cobalt form magnets that retain useful strength at elevated temperatures.
Meet Cobalt (Co)Properties and conditions
- Standard atomic weight
- 150.36(2)CIAAW 2024 standard atomic weight (dimensionless). Parentheses give uncertainty in the last quoted digits. Source flags: g.CIAAW standard atomic weights ↗ · Retrieved 2026-10-15
- Standard state
- SolidPubChem classification, including explicit predictions where stated. Reference temperature and pressure are not supplied in the table.PubChem periodic table ↗ · Retrieved 2026-10-15
- First ionisation energy
- 5.644 eVEnergy to remove the first electron from an isolated neutral gas-phase atom. Uncertainty is not supplied.PubChem periodic table ↗ · Retrieved 2026-10-15
- Electronegativity
- 1.17 Pauling scaleA dimensionless relative measure; values depend on the chosen scale. Uncertainty is not supplied.PubChem periodic table ↗ · Retrieved 2026-10-15
- Melting point
- 1347 KPubChem reported value. Pressure, allotrope and measurement uncertainty are not specified in the table; consult the cited source.PubChem periodic table ↗ · Retrieved 2026-10-15
- Boiling point
- 2067 KPubChem reported value. Pressure and measurement uncertainty are not specified in the table; consult the cited source.PubChem periodic table ↗ · Retrieved 2026-10-15
- Density
- 7.52 g/cm³PubChem reported value. Temperature, pressure, allotrope and measurement uncertainty are not specified in the table; gas densities are especially condition-dependent.PubChem periodic table ↗ · Retrieved 2026-10-15
- Oxidation states
- +3, +2Selected PubChem oxidation states; formal electron bookkeeping, not a list of stable free-ion charges or every possible compound.PubChem periodic table ↗ · Retrieved 2026-10-15
- Discovery
- 1879PubChem discovery attribution. Ancient knowledge and competing priority claims cannot always be represented by a single year.PubChem periodic table ↗ · Retrieved 2026-10-15
- Atomic radius
- 229 pmPubChem tabulated radius. Radius definitions depend on bonding and convention; measurement definition and uncertainty are not supplied in this table.PubChem periodic table ↗ · Retrieved 2026-10-15
- Electron affinity
- Not reportedPubChem reported gas-phase electron affinity. Sign conventions and electronic states matter; uncertainty is not supplied in this table.PubChem periodic table ↗ · Retrieved 2026-10-15
Isotopes, abundance and decay
Isotopes share a proton count but have different neutron counts. This selection includes naturally tabulated compositions and a reference isotope for other elements. It is not a list of every known isotope.
Explore 7 isotopes of Sm
| Isotope | Relative atomic mass | Natural fraction | Half-life | Decay |
|---|---|---|---|---|
| Sm-144 | 143.9120065(21) | 0.0307(7) | No decay observed | ;2β+ ? |
| Sm-147 | 146.9149044(19) | 0.1499(18) | 106.6 Gy (uncertainty 0.5) | ;α=100 |
| Sm-148 | 147.9148292(19) | 0.1124(10) | 6.3 Py (uncertainty 1.3) | ;α=100 |
| Sm-149 | 148.9171921(18) | 0.1382(7) | No decay observed | ;A ? |
| Sm-150 | 149.9172829(18) | 0.0738(1) | No decay observed | No decay tabulated |
| Sm-152 | 151.9197397(18) | 0.2675(16) | No decay observed | No decay tabulated |
| Sm-154 | 153.9222169(20) | 0.2275(29) | No decay observed | ;2β− ? |
Fractions use NIST’s terrestrial isotopic compositions, which can vary by sample. Parentheses denote uncertainty in the last digits. Half-lives and decay branches use NUBASE2020; # marks estimates, >/< mark limits. “No decay observed” follows that evaluation and does not prove permanent stability. Decay branch intensities are percentages; SF means spontaneous fission, EC electron capture, IT an isomeric transition.
Follow the science
Use these original references to explore the data and context. Atomic weights can vary with isotope composition; values for elements without stable isotopes may describe a representative isotope rather than a standard atomic weight.