Chemistry

An Overview about the Chemical Element Promethium



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Promethium

Symbol: Pm

Atomic Number: 61

Atomic Mass: 145.0 amu (atomic mass units)

Melting Point: 1042C (1315 K, 1908F)

Boiling Point: 3000C (3273 K, 5432F)

Number of Protons: 61

Number of Electrons: 61

Number of Neutrons: 84

Classification: Rare Earth Metal (Man Made)

Group name: Lanthanoid or lanthanide

Crystal Structure: Hexagonal

Density @ 293 K: 6.475 grams per cubic centimeter

Color: Unknown

In 1902 Banner predicted the existence of element 61. There were claims that it had been found dating from 1924 none of which could be substantiated. In 1944 Jacob A. Marinsky, Lawrence E. Glendenin and Charles D. Coryell were examining the by products of the nuclear reactor based at Clinton Laboratories in Oak Ridge, Tennessee (now the Oak Ridge National Laboratory). Within these by products they found the long sort after element 61 by using ion-exchange chromatography. Owing to security concerns with the ongoing world war the announcement of their discovery was not made until 1946. The element is named after Prometheus a figure from Greek mythology who stole fire from the gods.

Promethium is a highly radioactive element. Salts containing promethium show luminescence giving of a pale green or pale blue glow owing to the elements radioactivity. The element has an ionization energy of 5.55 eV and an oxidation state of +3. It is the only rare earth element of the lanthanide series which is man made all the others have been found within mineral ores. While not found on earth spectroscopic observations of a star in the constellation Andromeda has revealed that promethium exists in at least one star in the universe.

There are no stable isotopes of promethium. A number of isotopes with mass numbers ranging from 128 to 163 have been made. The most stable isotope produced to date is promethium-145. Prometium145 has a half-life of 17.7 years and decays to form neodymium-145 by electron capture.

Today promethium is still obtained from the chain reaction of uranium in nuclear reactors. It can also be produced from neodymium-146. If neodymium-146 is bombarded with neutrons it forms neodymium-147. Neodymium-147 has a half-life of 11 days and it decays by beta decay to form promethium-147.

At present promethium has no industrial use. It does have the potential to be used in some new technologies.

It could be used to make nuclear batteries. The beta particles emitted by some isotopes of promethium could activate a phosphor the light from the phosphor would then impact a photocell which would produce power in a similar manner to solar cells. It is thought that such a battery would produce power for up to five years.

Other possible applications include use as a portable X-ray source or in radioisotope thermoelectric generators to power space craft. It could also be used as a radioactivity source for thickness gauges or in the laser technology used for communication with submarines.

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