Periodic table › Samarium
Samarium — Sm
Lanthanoid · Group Lanthanoid (f-block) · Period 6
Open the 3D atom, orbital and crystal lab →1. Identity and classification
Silvery-white, malleable, electropositive rare-earth metal that tarnishes in air
- Name and symbol
- Samarium (Samarium) · Sm
- Atomic number
- 62
- Relative atomic weight / mass number
- 150.36 ± 0.02
- Group · period · block
- Lanthanoid (f-block) · 6 · f
- Category
- Lanthanoid
- State near room temperature
- Solid
- Stable isotopes
- At least one stable isotope
- CAS number
- 7440-19-9
Square brackets [A] indicate a representative isotope mass number, not an average atomic weight. Neutron counts differ between isotopes.
2. Atomic structure and electron configuration
- Protons · electrons in a neutral atom
- 62 · 62
- Neutrons in reference isotope
- 90 (152Sm)
- Full electron configuration
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 4f⁶ 6s²- Abbreviated configuration
[Xe]6s² 4f⁶- Electrons per shell
- 2, 8, 18, 24, 8, 2
- Listed oxidation states
- +3, +2
- Electronegativity
- 1.17 (Pauling)
- First ionization energy
- 544.563 kJ/mol · 5.644 eV
- Electron affinity
- Not established
- Covalent radius
- 198 pm
- van der Waals radius
- 229 pm
Configurations of superheavy elements may include theoretical predictions. Different definitions of atomic radius are not interchangeable.
3. Physical and thermal properties
- Density
- 7.52 g/cm³
- Melting point
- 1347 K · 1073.85 °C · 1964.93 °F
- Boiling point
- 2067 K · 1793.85 °C · 3260.93 °F
- Crystal structure
- Rhombohedral
- Specific heat
- 0.197 J/(g·K)
- Thermal conductivity
- 13.3 W/(m·K)
- Enthalpy of fusion
- 8.62 kJ/mol
- Enthalpy of vaporization
- 165 kJ/mol
- Magnetic ordering
- Paramagnetic
- Mohs hardness
- Not established
- Speed of sound
- 2130 m/s
Density and structure depend on temperature, pressure and allotrope. 25°C is a room-temperature reference, not STP. Unestablished values are not zero.
4. Chemical behavior and compounds
The +3 state is common in this series, with important element-specific exceptions.
Selected compounds: SmO / Sm₂O₃ (Oxide) · SmClₙ (Chloride) · SmFₙ (Fluoride)
Reaction reference
Many members oxidize in air; behavior depends on the element and oxidation state.
Water reactivity varies across this series and with surface conditions.
5. Isotopes
| Isotope | Status | Natural abundance | Half-life |
|---|---|---|---|
| 144Sm | Stable | 3.08% | Stable |
| 147Sm | Radioactive | 15.00% | 1.073E11 Y |
| 148Sm | Radioactive | 11.25% | 7E+15 Y |
| 149Sm | Stable | 13.82% | Stable |
| 150Sm | Stable | 7.37% | Stable |
| 151Sm | Radioactive | — | 90 Y |
| 152Sm | Stable | 26.74% | Stable |
| 154Sm | Stable | 22.74% | Stable |
Half-life units: s seconds, m minutes, h hours, d days, Y years. A dash means no natural-abundance value is given, not zero. Listed records are selected ground states; metastable states are distinct.
6. Discovery and occurrence
- Discovery
- 1879 CE
- Scientists associated with discovery
- Paul-Émile Lecoq de Boisbaudran
- Location
- France (Paris)
- Origin
- Natural
- Listed crustal abundance
- Not established
Minerals and naming reference
Bastnäsite, Monazite, Samarskite
Named from scientific/historical roots associated with Samarium (Sm), discovered or characterized by Paul-Émile Lecoq de Boisbaudran.
7. Applications
Samarium-Cobalt (SmCo₅ / Sm₂Co₁₇) permanent magnets that retain magnetism at high temperatures (>300 °C), ¹⁵³Sm bone cancer pain palliation
Detailed applications by field
- everyday
- Samarium-Cobalt (SmCo₅ / Sm₂Co₁₇) permanent magnets that retain magnetism at high temperatures (>300 °C), ¹⁵³Sm bone cancer pain palliation
- industry
- Used in lanthanoid processing, specialized alloys, and chemical manufacturing (Samarium-Cobalt (SmCo₅ / Sm₂Co₁₇) permanent magnets that retain magnetism at high temperatures (>300 °C), ¹⁵³Sm bone cancer pain palliation).
- electronics
- Applied in electronic components, semiconductors, or functional coatings where Samarium's electronic structure ([Xe] 4f⁶ 6s²) provides target conductivity.
- medicine
- Diagnostic imaging, biomedical instrumentation, or pharmaceutical synthesis research.
- energy
- Utilized in power generation, battery materials, catalysts, or nuclear technology involving Samarium.
- aerospace
- High-performance materials, structural alloys, or space instrumentation utilizing Samarium.
- agriculture
- Soil geochemistry analysis, trace micronutrient research, or analytical environmental monitoring.
- science
- Spectroscopic standard, crystallography, and quantum chemistry studies of Period 6 f-block elements.
8. Biological role and safety
Hazard depends on the isotope, chemical form, dose and exposure route.
Elemental substances, ions, compounds and radioisotopes can have different health effects. This is an educational reference; laboratory work requires the material safety data sheet and trained supervision.
Biological role reference
Classified as non-essential in human and biological systems.