Introduction
Promethium (atomic number 61) is the outlier among the rare earths. It is the only one that is radioactive and does not occur naturally on Earth in any significant quantity. It was the last of the lanthanides to be discovered and is generally produced synthetically.
Chemical & Physical Properties
A silvery metal that is highly radioactive. It emits beta radiation. Because of its intense radioactivity, its chemical properties are difficult to study extensively, though they generally align with neighboring lanthanides.
Occurrence & Production
Promethium is not mined. Minute traces exist in uranium ores as a product of spontaneous fission, but it is commercially produced by bombarding Neodymium-146 with neutrons in nuclear reactors to create Promethium-147.
Key Applications & Uses
Due to its radioactivity and scarcity, its uses are highly specialized:
- Nuclear Batteries: Its beta decay is used to generate heat, which is converted into electricity in radioisotope thermoelectric generators (RTGs). These long-life atomic batteries are used in spacecraft, guided missiles, and occasionally pacemakers (though lithium batteries have mostly replaced them here).
- Luminous Paint: Formerly used in luminous dials for watches, though largely replaced by safer tritium.
Future Outlook & Significance
Promethium remains a niche element with highly specialized applications in aerospace and defense due to its unique nuclear properties.