[[Chemistry]] | [[1940s]] Promethium (symbol: **Pm**, atomic number: **61**) is a rare earth element belonging to the **lanthanide series** of the periodic table. It holds the distinction of being the **only radioactive lanthanide** and one of only two elements below atomic number 83 (bismuth) that have **no stable isotopes** — the other being technetium (43). --- ## Discovery & History ### The Hunt for Element 61 The existence of element 61 was predicted long before its discovery. The periodic table had a conspicuous gap between neodymium (60) and samarium (62), and chemists had been searching for the missing element since the early 20th century. Several false claims of discovery were made: - **1926** — Italian scientists claimed discovery and named it _Florentium_ - **1926** — American researchers claimed discovery and named it _Illinium_ Both claims were ultimately invalidated due to insufficient evidence and contaminated samples. ### Confirmed Discovery — 1945 Promethium was conclusively identified in **1945** at **Oak Ridge National Laboratory** by **Jacob A. Marinsky**, **Lawrence E. Glendenin**, and **Charles D. Coryell**. They isolated it from the fission products of uranium in a nuclear reactor — a direct byproduct of the **Manhattan Project's** wartime nuclear research infrastructure. The element was named after **Prometheus**, the Titan of Greek mythology who stole fire from the gods and gave it to humanity — a deliberate nod to the **harnessing of nuclear fire** that made its discovery possible. Coryell's wife, Grace Mary Coryell, is credited with suggesting the name. --- ## Physical & Chemical Properties - **Category:** Lanthanide / Rare Earth Metal - **Appearance:** Metallic, likely silvery-white (rarely observed in pure form) - **Most stable isotope:** Pm-145 (half-life ~17.7 years) - **Most commonly used isotope:** Pm-147 (half-life ~2.62 years, beta emitter) - **Natural occurrence:** Essentially zero — only trace amounts exist in nature as a result of spontaneous fission of uranium and neutron capture in uranium ores. Estimated total natural occurrence on Earth: **less than 1 kilogram** at any given time - **Production:** Almost entirely synthetic, produced in nuclear reactors via neutron bombardment of neodymium or as a fission byproduct --- ## Applications Despite its rarity and radioactivity, Pm-147 has had several notable practical uses: ### Nuclear Batteries (Betavoltaics) Pm-147's beta radiation can be converted directly into electricity. This made it valuable for **radioisotope thermoelectric generators (RTGs)** and betavoltaic devices used in: - Early **cardiac pacemakers** (before lithium batteries became standard) - **Spacecraft and satellite** power systems - Remote sensing equipment in isolated environments ### Luminous Paint & Gauges Promethium was used in **self-luminous paints** for instrument dials, gauges, and military equipment — similar in application to radium but with a shorter half-life making it somewhat more manageable from a radiation exposure standpoint. ### Thickness Measurement Industrial applications include **beta radiation gauges** used to measure the thickness of thin materials like plastic film, paper, and metal sheeting during manufacturing. ### X-Ray Sources Portable, compact X-ray sources using Pm-147 have been used in field applications where conventional X-ray equipment is impractical. --- ## Geopolitical Implications ### Nuclear Program Byproduct Promethium's existence is fundamentally tied to **nuclear reactor and weapons program infrastructure**. Its discovery emerged directly from Manhattan Project research, and its production requires access to nuclear reactors. This means: - Nations with advanced nuclear programs have implicit access to promethium production - It serves as a quiet indicator of **nuclear technological sophistication** - Its applications in military instrumentation have historically given it minor but real **defense significance** ### Rare Earth Supply Chain Context While promethium is not traded in rare earth markets the way neodymium or dysprosium are (due to its radioactivity and synthetic production), it sits within the broader **rare earth geopolitical landscape** dominated by China. China controls roughly **60–70%** of global rare earth mining and a significant share of processing. Promethium's synthetic production partially insulates it from this dynamic, but the broader lanthanide supply chain dependency remains a strategic concern for the U.S. and allied nations. ### Oak Ridge & U.S. Nuclear Infrastructure The fact that promethium was discovered and is primarily produced at **Oak Ridge National Laboratory** in Tennessee connects it to ongoing debates about U.S. investment in nuclear infrastructure. Oak Ridge remains a critical node in America's nuclear research and isotope production ecosystem — increasingly important as the U.S. seeks to reduce dependency on Russian-supplied isotopes following sanctions related to the **Ukraine conflict**. --- ## Current Research & Significance In **2024**, researchers at Oak Ridge made headlines by successfully producing and studying a **soluble promethium complex** for the first time — providing new insights into the chemical behavior of lanthanides. This closed a long-standing gap in lanthanide chemistry research and has potential implications for: - Better understanding of **nuclear waste processing** - Advances in **rare earth separation chemistry** - Potential new medical and industrial isotope applications --- ## Summary Promethium is a scientific curiosity that sits at the intersection of **nuclear history, Cold War technology, and rare earth geopolitics**. Born from the atomic age, it remains one of the least understood and most difficult to study elements on the periodic table — yet its applications have quietly touched everything from the human heart (pacemakers) to outer space (satellite power). Its story is inseparable from the history of nuclear technology and the institutions — particularly Oak Ridge — that defined 20th century American scientific power.