61
Promethium
Atomic Number61
Atomic Mass145 u
CategoryLanthanide
State at Room TempSolid
Year Discovered1945
About Promethium
The only radioactive lanthanide with no stable isotopes. Barely half a kilogram exists in the entire crust at any moment, formed by uranium decay and star explosions. Named after Prometheus, who stole fire from the gods. Used in luminous paint, nuclear batteries for missiles and pacemakers, and thickness gauges. First identified in residues from uranium fission.
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