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Promethium Facts

Chemical & Physical Properties


Promethium is a radioactive rare earth element.

Promethium is a radioactive rare earth element.

Justin Urgitis
Periodic Table of the Elements


Atomic Number: 61

Symbol: Pm

Atomic Weight: 144.9127

Element Classification: Rare Earth Element (Lanthanide Series)

Discoverer: J.A. Marinsky, L.E. Glendenin, C.D. Coryell

Discovery Date: 1945 (United States)

Name Origin: Named for the Greek god, Prometheus

Density (g/cc): 7.2

Melting Point (K): 1441

Boiling Point (K): 3000

Covalent Radius (pm): 163

Ionic Radius: 97.9 (+3e)

Specific Heat (@20°C J/g mol): 0.185

Pauling Negativity Number: 0.0

First Ionizing Energy (kJ/mol): 536

Oxidation States: 3

Electronic Configuration: [Xe] 4f5 6s2

References: Los Alamos National Laboratory (2001), Crescent Chemical Company (2001)


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