Samarium (Sm)
Element 62 · Lanthanide · atomic mass 150.36 u · f-block, period 6
Electron shells: 2, 8, 18, 24, 8, 2
Samarium-cobalt magnets hold their strength at temperatures that would demagnetise neodymium. That makes them the choice for military and aerospace hardware.
Its mineral was named for Vasili Samarsky-Bykhovets, then alive — making samarium the first element named, if indirectly, for a living person.
- Atomic number
- 62
- Atomic mass
- 150.36 u
- Electron configuration
- [Xe] 6s² 4f⁶
- Group · period · block
- f-block · 6 · f
- Oxidation states
- +2, +3
- Electronegativity
- 1.17 (Pauling)
- Melting point
- 1,074 °C
- Boiling point
- 1,794 °C
- Density
- 7.52 g/cm³
- State at 20 °C
- Solid
- Appearance
- Silvery-white metal
- Discovered
- Paul-Émile Lecoq de Boisbaudran, 1879
62 protons, and 62 electrons when neutral
IUPAC standard atomic weight
Shown in the strip below the table
What Samarium is used for
- High-temperature permanent magnets
- Neutron-absorbing reactor rods
- Cancer treatment isotopes
- Optical glass and lasers
Atomic structure of Samarium
A neutral samarium atom has 62 protons and 62 electrons. Its most common isotope carries about 88 neutrons, which is where the mass number 150 comes from. Change the neutron count and you have a different isotope of samarium; change the proton count and you have a different element entirely.
Those electrons fill shells from the inside out: 2, 8, 18, 24, 8, 2. In orbital notation that is [Xe] 6s² 4f⁶. As a f-block element its valence count is variable, which is why it can form compounds in several oxidation states.
3D electron orbitals
See where Samarium's electrons actually are — a cloud of 26,000 points sampled from the probability density |ψ|², not a cartoon of a lobe.
Where Samarium sits in the periodic table
The first f-block row, elements 57-71. Chemically near-identical to each other and hard to separate, yet essential to magnets, lasers and phosphors.
- One proton lighter: Promethium.
- One proton heavier: Europium.
Discovery and naming
Samarium was discovered by Paul-Émile Lecoq de Boisbaudran in 1879. Its name comes from The mineral samarskite, which is also why its symbol (Sm) does not match its English name.
Keep exploring
Atomic weight from IUPAC/CIAAW; physical properties from PubChem (US National Library of Medicine). Values that have never been measured are shown as “not measured” rather than estimated.
Related Calculators
Frequently Asked Questions
What is the atomic mass of Samarium?
The standard atomic weight of Samarium is 150.36 u, as published by IUPAC's Commission on Isotopic Abundances and Atomic Weights.
How many protons, neutrons and electrons does Samarium have?
Samarium has 62 protons, because the atomic number is the proton count and that is what makes an atom Samarium at all. A neutral Samarium atom has the same number of electrons, 62. The neutron count varies by isotope; the most common one has about 88, since 150 − 62 = 88.
What is the electron configuration of Samarium?
The electron configuration of Samarium is [Xe] 6s² 4f⁶. Its electrons are arranged 2, 8, 18, 24, 8, 2 across 6 shells.
Is Samarium a metal?
Yes. Samarium is classified as a lanthanide, on the metallic side of the table.
What group and period is Samarium in?
Samarium sits in the f-block strip below the main table, in period 6, among the lanthanides. Elements in that strip are not given a group number in the standard 18-column layout.
What is the charge of Samarium?
Samarium most commonly forms a 3+ ion. Like most transition metals it has several accessible oxidation states, so the charge depends on the compound. Across all its compounds it shows oxidation states of +2, +3.
What is the melting point of Samarium?
Samarium melts at 1,074 °C and boils at 1,794 °C. That puts it in the solids at everyday temperatures.
What is Samarium used for?
High-temperature permanent magnets, Neutron-absorbing reactor rods, Cancer treatment isotopes, Optical glass and lasers. Samarium-cobalt magnets hold their strength at temperatures that would demagnetise neodymium.
Who discovered Samarium, and where does its name come from?
Samarium (Sm) was discovered by Paul-Émile Lecoq de Boisbaudran in 1879. The name comes from The mineral samarskite.