Samarium (Sm)

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.
Atomic Number62
Atomic Weight150.36
Mass Number152
Protons62 p+
Neutrons90 n0
Electrons62 e-
Samarium 1.jpg Animated Bohr Model Enhanced Bohr Model Bohr Model Orbital Diagram


Atomic Radius
185 pm
Atomic Volume
Covalent Radius
172 pm
Metallic Radius
Ionic Radius
122 pm
Crystal Radius
136 pm
Van der Waals radius
236 pm
7.52 g/cm³
Boiling Point
2,064 K
Melting Point
1,350 K
Electrons per shell2, 8, 18, 24, 8, 2
Proton Affinity
Electron Affinity
Ionization Potential
5.64371 eV/particle
Heat of Vaporization
165 kJ/mol
Heat of Fusion
8.9 kJ/mol
Heat of Formation
206.7 kJ/mol
Molar Heat Capacity
29.54 J/(mol K)
Specific Heat Capacity
0.197 J/(g⋅K)
Thermal Conductivity
Gas Basicity
Dipole Polarizability
192 a₀
C6 Dispersion Coefficient
Oxidation States2, 3
Crystal StructureSimple Trigonal (RHL)
Lattice Constant
9 Å
Bulk Modulus
Electrical Resistivity
Electron Configuration[Xe] 4f6 6s2
Magnetic Ordering
Magnetic Susceptibility
Poisson Ratio
Shear Modulus
Young's Modulus
Alternate Names
Adiabatic Index
Electric Conductivity
Critical Pressure
Critical Temperature
Curie Point
Magnetic Susceptibility
Neel Point
Neutron Cross Section
Neutron Mass Absorption
Gas Phase
Quantum Numbers
Refractive Index
Space Group
Speed of Sound
Superconducting Point
Thermal Expansion
Valence Electrons
CategoryLanthanides, Lanthanides
CAS Group
Glawe Number27
Mendeleev Number23
Pettifor Number28
Geochemical Classrare earth & related
Goldschmidt Classlitophile
Decay Mode
Abundance in Earth's crust
7.05 mg/kg
Abundance in Oceans
0.00000045 mg/L
Abundance in Human Body
Abundance in Meteor
Abundance in Sun
Abundance in Universe5×10-7%

Isotopes of Samarium

Stable Isotopes
144Sm 147Sm 148Sm 149Sm 150Sm 152Sm 154Sm
Unstable Isotopes
128Sm 129Sm 130Sm 131Sm 132Sm 133Sm 134Sm 135Sm 136Sm 137Sm 138Sm 139Sm 140Sm 141Sm 142Sm 143Sm 145Sm 146Sm 151Sm 153Sm 155Sm 156Sm 157Sm 158Sm 159Sm 160Sm 161Sm 162Sm 163Sm 164Sm 165Sm


In 1853, Jean Charles Galissard de Marignac discovered samarium when he found lines in mineral spectra. Paul Émile Lecoq de Boisbaudran isolated a samarium salt in Paris in 1879 from the mineral samarskite and identified a new element in it via sharp optical absorption lines. The pure element was produced only in 1901 by Eugène-Anatole Demarçay. From samarskite, a mineral named after Russian mine official, Col. Samarski

DiscoverersPaul Émile Lecoq de Boisbaudran
Discovery LocationFrance
Discovery Year1879
Name OriginNamed after the mineral samarskite.
Samarium is considered to be moderately toxic
Samarium metal can be produced by reducing the oxide with lanthanum


Samarium's main use is in samarium-cobalt alloy magnets for headphones, small motors and pickups for some electric guitars. Radioactive samarium-153 is used to kill cancer cells in the treatment of lung cancer, prostate cancer, breast cancer and osteosarcoma. Samarium and its compounds are also used as catalyst and chemical reagent. It is used in the electronics and ceramics industries. It is easily magnetized and very difficult to demagnetize. This suggests important future applications in solid-state and superconductor technologies.


Found with other rare earths in monazite sand. The sand is often 50% rare earths by weight and 2.8% samarium.