Promethium Facts

Learn more about Promethium or Pm Chemical & physical properties

Promethium is a radioactive rare earth element
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Promethium is a radioactive rare earth metal. Here's a collection of interesting promethium element facts:

Interesting Promethium Facts

  • The original spelling of the name promethium was prometheum.
  • The element is named for Prometheus, the Titan who stole fire from the Greek gods to give to mankind.
  • Promethium was the last rare earth element of the lanthanide series to be discovered. It was discovered in 1945 by Jacob A. Marinsky, Lawrence E. Glendenin, and Charles D. Coryell, although its existence had been predicted in 1902 by Czech chemist Bohuslav Brauner. Marinsky's group found promethium in uranium fission products during Manhattan Project research in Oak Ridge, TN.
  • All of the isotopes of promethium are radioactive. It is the only radioactive rare earth metal and it is one of only two radioactive elements followed by stable elements on the periodic table. The other element like this is technetium.
  • Promethium isotopes generate x-rays via beta decay. 29 isotopes are known, with mass numbers from 130 to 158.
  • Promethium is prepared in a lab. It is extremely rare on Earth, although it has been detected in pitchblende specimens from the radioactive decay of uranium.
  • The only stable oxidation state of promethium is 3+, although it can be made to display the 2+ oxidation state. This is common with lanthanide elements.
  • The pure metal has a silvery appearance. Salts of promethium glow pale blue or green, due to radioactive decay.
  • Because of its radioactivity, promethium is considered toxic.
  • Promethium compounds have several practical applications, all more to deal with its radioactivity than its chemical properties. The earliest pacemakers used nuclear batteries that relied on promethium. It is used in missile and spacecraft power sources, as a beta source for thickness gauges, and to make luminous paints.

Promethium Chemical and Physical Properties

Element Name: Promethium

Atomic Number: 61

Symbol: Pm

Atomic Weight: 144.9127

Element Classification: Rare Earth Element (Lanthanide Series)

Discoverer: J.A. Marinsky, L.E. Glendenin, C.D. Coryell

Discovery Date: 1945 (United States)

Name Origin: Named for the Greek god, Prometheus

Density (g/cc): 7.2

Melting Point (K): 1441

Boiling Point (K): 3000

Covalent Radius (pm): 163

Ionic Radius: 97.9 (+3e)

Specific Heat (@20°C J/g mol): 0.185

Pauling Negativity Number: 0.0

First Ionizing Energy (kJ/mol): 536

Oxidation States: 3

Electronic Configuration: [Xe] 4f5 6s2

References: Los Alamos National Laboratory (2001), Crescent Chemical Company (2001)

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