Promethium (Pm)

Joanna Mantsevich

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Atomic Structure

Atomic Number: 61

Mass Number: 145

Protons: 61

Neutrons: 84

Electrons: 61

Physical Properties

Atomic Mass: 145

Atomic Radius in picometers (pm): 205pm

Density: 7.264 g/cc

Melting Point: 1100°C (2010°F)

Boiling Point: 3000°C (5430°F)

At room temperature (22°C), this element is a: Solid

Appearance: Metallic

Conductivity: Thermal: 17.9 W m-1 K-1 Electrical: 2 x 106 S m-1

Malleability: It is malleable.

Hardness: N/A

Other physical properties: Radioactive, Rare Earth

Chemical Properties

Flammability: N/A

Reactivity: Highly; Radioactive

Where in the universe?

Promethium can be found in space. It is not found on Earth, but scientist can produce it artificially in a particle accelerator. It can be found in space.


Promethium has 38 isotopes with half-lives that are known with masses from 130 to 158. Its longest lived isotope is promethium-145 which lived for 17.7 years.


Promethium and oxygen can combine together to make Pm2O3 which is the most common form of Promethium.Promethium and chloride can combine to make PmCl3.

Discovery and Naming

Promethiums existence was first predicted by Bohuslav Brauner in 1902. Chemist B. Smith Hopkins claimed that the element had been found in rare-earth residues and named it illinium, but around the same time, Luigi Rolla and Rita Brunetti also claimed to have discovered it they chose the name florentium for it. Jacob A. Marinsky, Lawrence E. Glendenin and Charles D. Coryell produced firm evidence in 1945 in Oak Ridge, Tennessee. They named it Promethium.

What can it be used for?

Fun Facts


Element Card: Gray, Theodore W. (2008). The Photographic Card Deck of the Elements.

Elements Book: Gray, Theodore W. (2009). The Elements: A visual exploration of every known atom in the universe. New York: Black Dog & Leventhal Publishers, Inc.

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