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It's Elemental

The Element Promethium

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61 Pm Promethium 145

Atomic Number: 61

Atomic Weight: 145

Melting Point: 1315 K (1042°C or 1908°F)

Boiling Point: 3273 K (3000°C or 5432°F)

Density: 7.26 grams per cubic centimeter

Phase at Room Temperature: Solid

Element Classification: Metal

Period Number: 6

Group Number: none

Group Name: Lanthanide

Special Notes: Radioactive and Artificially Produced

What's in a name? Named for the Greek mythological figure Prometheus.

Say what? Promethium is pronounced as pro-MEE-thee-em.

History and Uses:

The existence of promethium was predicted by Bohuslav Brauner, a Czech chemist, in 1902. Several groups claimed to have produced the element, but they could not confirm their discoveries because of the difficulty of separating promethium from other elements. Proof of the existence of promethium was obtained by Jacob A. Marinsky, Lawrence E. Glendenin and Charles D. Coryell in 1944. Too busy with defense related research in World War II, they did not claim their discovery until 1946. They discovered promethium while analyzing the byproducts of uranium fission that were produced in a nuclear reactor located at Clinton Laboratories in Oak Ridge, Tennessee. Today, Clinton Laboratories is known as Oak Ridge National Laboratory.

Today, promethium is still recovered from the byproducts of uranium fission. It can also be produced by bombarding neodymium-146 with neutrons. Neodymium-146 becomes neodymium-147 when it captures a neutron. Neodymium-147, with a half-life of 11 days, decays into promethium-147 through beta decay. Promethium does not occur naturally on earth, although it has been detected in the spectrum of a star in the constellation Andromeda.

Promethium's most stable isotope, promethium-145, has a half-life of 17.7 years. It decays into neodymium-145 through electron capture.

Promethium could be used to make a nuclear powered battery. This type of battery would use the beta particles emitted by the decay of promethium to make a phosphor give off light. This light would then be converted into electricity by a device similar to a solar cell. It is expected that this type of battery could provide power for five years.

Promethium could also be used as a portable X-ray source, in radioisotope thermoelectric generators to provide electricity for space probes and satellites, as a source of radioactivity for gauges that measure thickness and to make lasers that can be used to communicate with submerged submarines.

Estimated Crustal Abundance: Not Applicable

Estimated Oceanic Abundance: Not Applicable

Number of Stable Isotopes: 0 (View all isotope data)

Ionization Energy: 5.55 eV

Oxidation States: +3

Electron Shell Configuration:


2s2   2p6

3s2   3p6   3d10

4s2   4p6   4d10   4f5

5s2   5p6


Citation and linking information

For questions about this page, please contact Steve Gagnon.