Samarium
Definition and meaning of Samarium in chemistry.
![Samarium element card: symbol Sm, atomic number 62, atomic mass 150.36, electron configuration [Xe] 4f⁶ 6s², oxidation states +3, Lanthanide, f-block, period 6, solid at room temperature.](/assets/images/terms/samarium-chemical-element.webp)
Samarium is a silvery-white rare-earth metal with the chemical symbol Sm and atomic number 62. It belongs to the lanthanide series, which is a group of elements found near the bottom of the periodic table. This reactive metal slowly tarnishes in moist air and easily catches fire at 150 degrees Celsius.
In more detail
Samarium sits in the f-block of the periodic table, where atoms fill their inner f-orbitals with electrons. In most chemical compounds, samarium atoms lose three electrons to form ions with a +3 charge. These compounds usually look pale yellow when dissolved in water or sitting on a lab shelf.
However, samarium can also form stable compounds with a +2 charge. This low charge is very unusual for lanthanide elements, which typically prefer the +3 state. A great example of this is samarium(II) iodide, a useful compound that chemists call Kagan's reagent.
This compound acts as a powerful reducing agent by giving away single electrons to other molecules. Chemists use it in organic synthesis to build complex structures by linking carbon atoms. In nature, samarium never exists as a pure metal because it is too reactive.
Instead, it hides inside complex minerals such as monazite and bastnasite. Mining companies use acid treatments and solvent extraction to separate samarium from other rare metals. A common student misconception is that rare-earth elements are extremely scarce in the earth.
Actually, samarium is more common than metals like tin or cobalt. Pure samarium is also highly effective at absorbing neutrons, which are neutral particles inside atom nuclei. This property makes it perfect for control rods that regulate nuclear reactions inside power plants. The metal is also naturally magnetic, although its magnetic pull is weaker than other rare-earth metals.
Key facts
| Field | General Chemistry |
|---|---|
| Symbol | Sm |
| Atomic number | 62 |
| Atomic mass | 150.36 u |
| Category | Lanthanide |
| State at room temperature | Solid |
Engineers mix samarium with cobalt to make permanent magnets for space satellites and high-tech weapons. These samarium-cobalt magnets are highly valued because they resist demagnetization at extreme temperatures. Unlike standard magnets, they keep their magnetic strength even when heated above 300 degrees Celsius.
Frequently asked questions
What is samarium(II) iodide used for?
Chemists often call this Kagan's reagent. It gives away single electrons in lab reactions. Scientists use it to build complex new molecules by joining carbon atoms together.
Is pure samarium metal magnetic on its own?
Pure samarium is only weakly magnetic at room temperature. It does not stick strongly to other magnets. However, it makes very strong permanent magnets when mixed with cobalt.
Why is samarium used in nuclear reactors?
It is excellent at capturing neutrons without breaking apart. This helps control the rate of nuclear fission reactions. Engineers build it into reactor control rods to keep the power plant safe.
Related terms
Sources & references
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