Promethium (Pm) - Discovery, Occurrence, Production, Properties and Applications of Promethium

Chemical Formula

Pm

Background

Bohuslav Brauner, a Czech chemist predicted the existence of promethium in 1902. Although several groups claimed to have discovered the element, none of them were able to confirm their discovery. However, Charles D. Coryell, Lawrence E. Glendenin and Jacob A. Marinsky proved the existence of promethium in 1944 and claimed their findings in 1946. They discovered promethium while examining the byproducts of uranium fission in a nuclear reactor at the Oak Ridge National Laboratory. The IUPAC named the element as promethium in 1949 after the Greek Titan Prometheus.

Basic Information

Name Promethium
Symbol Pm
Atomic number 61
Atomic weight 145 amu
Standard state Solid at 298 K
CAS Registry ID 12/2/7440
Group name Lanthanoid
Period in periodic table 6
Block in periodic table f-block
Color Metallic
Classification Metallic
Melting point 1315 K (1042°C or 1908°F)
Boiling point 3273 K (3000°C or 5432°F)
Density 7.26 g/cm3
Phase at room temperature Solid

Occurrence

Promethium is not found in the Earth’s crust. However, it can be observed in uranium ores as a product of uranium decay. In addition, it can be found in the Andromeda galaxy.

Isotopes

Promethium has 29 isotopes with mass numbers from 130Pm to 158Pm. It has no naturally-occurring isotopes. The longest-lived isotopes of promethium are 145Pm having a half-life of 17.7 years and 147Pm having a half-life of 2.6234 years.

Production

Pure promethium can be obtained through reducing promethium fluoride with calcium metal:

         2PmF3 + 3Ca → 2Pm + 3CaF2

Furthermore, a series of nuclear reactions involving bombardment of neodymium-146 with neutrons produced promethium. It can also be obtained from the byproducts of uranium fission.

Key Properties

The key properties of promethium are listed below:

  • It is a silvery-white radioactive metal
  • It luminesce with a pale blue or green glow in dark due to its radioactivity
  • It is very unstable
  • It is chemically similar to other lanthanides.

Applications

Some of the applications of promethium include the following:

  • It is used as a beta source for thickness gauges
  • It is used in atomic batteries suitable for radios, watches, missiles and spacecraft.

References

G.P. Thomas

Written by

G.P. Thomas

Gary graduated from the University of Manchester with a first-class honours degree in Geochemistry and a Masters in Earth Sciences. After working in the Australian mining industry, Gary decided to hang up his geology boots and turn his hand to writing. When he isn't developing topical and informative content, Gary can usually be found playing his beloved guitar, or watching Aston Villa FC snatch defeat from the jaws of victory.

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