Promethium

Promethium-147 solution

Pitchblende schlema-alberoda

Jacob A Marinsky

Larry E Glendenin

Charles D. Coryell M.I.T. May 1947

Pm,61

Promethium is a chemical element with the symbol Pm and atomic number 61. It is a rare and radioactive lanthanide, which is part of the periodic table's f-block. Promethium is notable for being the only lanthanide and one of the few elements that have no stable isotopes. All its isotopes are radioactive, and it is one of the two such elements that can be found in nature, the other being technetium. The most common isotopes of promethium are promethium-145, promethium-146, and promethium-147, with promethium-147 being the most abundant and widely used.

Properties

Promethium is a soft, silvery, metallic element that exhibits luminescence, emitting a pale blue or greenish glow in the dark when exposed to oxygen. This property makes it useful in certain types of radioluminescent materials. It has chemical properties typical of the lanthanides, forming trivalent ions (Pm^3+) that are usually colorless in solution.

Occurrence

Promethium is extremely rare in nature. It is found in trace amounts in the Earth's crust, primarily as a product of uranium decay and in some minerals that contain other rare earth elements. The element is more commonly obtained through nuclear reactors, where it is produced as a byproduct in the fission of uranium fuel.

Applications

Promethium's most significant application is in the production of batteries for use in space satellites and military equipment, where its radioactive decay provides a steady heat source that can be converted into electrical energy. These batteries, known as radioisotope thermoelectric generators (RTGs), can provide power for long durations, making them ideal for missions where solar power is not feasible. Promethium is also used in the manufacture of luminous paint, although this use has declined due to safety concerns associated with its radioactivity.

Health and Safety

As a radioactive element, promethium poses health risks if not handled properly. It can emit beta particles that are harmful to human tissue and can increase the risk of cancer upon prolonged exposure. Safety protocols involve shielding and strict regulatory controls to minimize exposure to promethium during its handling and transport.

History

Promethium was first identified in 1945 by Jacob A. Marinsky, Lawrence E. Glendenin, and Charles D. Coryell during their research on the fission products of uranium. The element was named after Prometheus, the Titan from Greek mythology who stole fire from the gods and gave it to humanity, symbolizing the use of promethium in providing energy.

Isotopes

All isotopes of promethium are radioactive. Promethium-147, with a half-life of about 2.62 years, is the most stable isotope. It decays into stable samarium-143 through beta decay. The radioactivity of promethium isotopes limits their use to applications where their radioactive properties can be beneficially employed.

See Also

• Lanthanides
• Radioactive decay
• Radioisotope thermoelectric generator
• Rare earth element

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