Samarium (Sm)

Samarium-cobalt magnets are weaker than neodymium ones but keep working past 300 °C and barely corrode, which is why they are used in jet engine actuators and in electric motors that run hot. Samarium-149 is one of the strongest neutron absorbers known and is a significant reactor poison — it builds up in fuel and eats into the chain reaction. The element was named after samarskite, the mineral it came from, which was itself named after a Russian mining official, making samarium arguably the first element named after a living person.

Properties

Atomic number

62

Symbol

Sm

Standard atomic weight

150.36 u

Category

Lanthanide

Period

6

Block

f-block

Electron configuration

[Xe] 6s² 4f⁶

Electrons per shell

2, 8, 18, 24, 8, 2

Melting point

1,347 K — 1073.8 °C — 1964.9 °F

Boiling point

2,067 K — 1793.8 °C — 3260.9 °F

Density

7.52 g/cm³

Electronegativity

1.17 (Pauling)

Oxidation states

+3, +2

Discovered

1879 by Paul-Émile Lecoq de Boisbaudran

Electron configuration

Full

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f⁶

Noble gas shorthand

[Xe] 6s² 4f⁶

Shells

K: 2 · L: 8 · M: 18 · N: 24 · O: 8 · P: 2

What it is used for

• Samarium-cobalt magnets for high-temperature motors and aerospace
• Neutron-absorbing control rods in reactors
• Samarium-153 for pain relief in bone cancer
• Catalysts for dehydrating and dehydrogenating alcohols
• Headphone drivers and pickup magnets that must not lose strength when hot

Neighbours in the table