The element named for the Greek Titan Prometheus is Promethium (Pm), atomic number 61. Promethium is a synthetic element, meaning it does not occur in nature in any significant quantity, which makes its name particularly fitting. Its existence was predicted decades before it was officially found, filling a gap in the periodic table between Neodymium and Samarium.
Identifying Element 61: Promethium
Promethium is classified as a lanthanide, placing it among the rare-earth elements. It is one of only two elements below lead (atomic number 82) that lacks any stable isotopes, meaning all its atomic forms are radioactive and decay over time. The other element is Technetium.
Promethium’s discovery is credited to American scientists Jacob Marinsky, Lawrence Glendenin, and Charles Coryell in 1945. The team isolated Promethium from the fission products of irradiated uranium fuel at Oak Ridge National Laboratory during the Manhattan Project. Due to military secrecy, the discovery was not formally announced until 1947, and the name was formally accepted in 1949. The most stable isotope, Promethium-145 (\(\text{Pm}-145\)), has a half-life of 17.7 years, which explains its extreme scarcity in the Earth’s crust.
The Gift of Fire: Why Promethium Shares the Name
The name Promethium was proposed by Grace Mary Coryell, the wife of one of the discoverers, to draw a direct parallel to the Greek myth. In mythology, the Titan Prometheus stole fire from the gods on Mount Olympus and delivered it to humanity, a gift that brought both progress and divine punishment. The scientists saw a powerful metaphor in this act of defiance and enlightenment.
The discovery of Promethium was a direct result of harnessing atomic fire—nuclear fission—a process that unlocks powerful new energies and materials. The element was essentially “stolen” from the destructive, controlled environment of a nuclear reactor, symbolizing the daring application of human intellect to a new force. The name was intended to symbolize both the scientific potential and the potential for misuse associated with atomic energy.
Radioactivity and Practical Presence
Promethium’s primary utility stems directly from its radioactivity, specifically its emission of beta particles. Because it has no stable isotopes, the element only occurs naturally in trace amounts, formed by the spontaneous fission of uranium ore. For practical applications, Promethium must be artificially synthesized, typically by processing nuclear reactor waste.
The most commonly used isotope, Promethium-147 (\(\text{Pm}-147\)), has a half-life of 2.62 years and is a relatively low-energy beta emitter. This property makes it suitable for use in radioluminescent paint, where its decay energy excites a phosphor to generate a sustained glow without an external power source. Historically, this luminous paint was used for instrument dials in aircraft, safety signs, and instrument illumination in the Apollo landing modules. Furthermore, \(\text{Pm}-147\) is used in compact nuclear batteries, known as betavoltaics, which provide long-lasting power for devices like pacemakers and specialized sensors.