Symbol Pm
Atomic Number 61
Atomic Mass (145) g.mol-1
Discovered by Mariinsky in 1945

Chemical Properties of Promethium

Group Lanthanides  Melting point 1042°C, 1908°F, 1315 K
Period 6 Boiling point 3000°C, 5432°F, 3273 K
Block f Density (g cm−3) 7.26
Atomic number 61 Relative atomic mass [145]
State at 20°C Solid Key isotopes 145Pm, 147Pm
Electron configuration [Xe] 4f56s2 CAS number 7440-12-2
ChemSpider ID 22386 ChemSpider is a free chemical structure database.

What is Promethium?

  • Promethium is a chemical element with the symbol Pm and atomic number 61 in the periodic table.
  • All of its isotopes are radioactive; it is one of only two such elements that are followed in the periodic table by elements with stable forms, a distinction shared with technetium.

Uses of Promethium

  • Most of the element is used only for research purposes, except for promethium-147, which can be found outside laboratories. This isotope does not emit gamma rays, and its radiation has a relatively small penetration depth into matter and a relatively long half-life.
  • Promethium is used in pacemakers. Some signal lights use a luminous paint containing phosphor that absorbs the beta radiation emitted by promethium-147 and emits light.

Properties of Promethium

  • Chemically, promethium is a lanthanide, which forms salts when combined with other elements. It shows only one stable oxidation state of +3.
  • Since traces of the element in nature is exceedingly scarce, the element is typically synthesized by bombarding enriched uranium with thermal neutrons to produce promethium-147.
  • Promethium salts have a pink or red color that colors the surrounding air with a pale blue-green light.

Certain Facts About Promethium

  • There is a strange star HR 465 in the Andromeda galaxy that contains a lot of Promethium. It is very radioactive and rare, so it is little studied: its chemical and physical properties are not well defined.

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