The Element Promethium
What is Promethium?
Promethium is a chemical element identified by the symbol Pm and atomic number 61. It is classified as a lanthanide, often referred to as a rare earth element. A defining characteristic of promethium is that all of its isotopes are radioactive, meaning their atomic nuclei are unstable and undergo spontaneous decay, emitting radiation. Because of this inherent instability and relatively short half-lives, promethium exists in extremely minute quantities in Earth’s crust, primarily as a by-product of uranium fission. This makes it one of the two elements below uranium (the other being technetium) that does not have any stable, non-radioactive isotopes.
Discovery and Naming
The existence of an element with atomic number 61 was predicted decades before its actual isolation. Promethium was definitively discovered and chemically characterized in 1945 by Jacob A. Marinsky, Lawrence E. Glendenin, and Charles D. Coryell at Oak Ridge National Laboratory in Tennessee, United States. Their work involved analyzing the by-products generated from the fission of uranium in a nuclear reactor, specifically during World War II efforts. The discovery was publicly announced after the war concluded.
The name “Promethium” was suggested by Grace Coryell, the wife of one of the discoverers, Charles Coryell. The name is derived from Prometheus, a prominent figure in ancient Greek mythology. Prometheus was a Titan celebrated for his act of stealing fire from the gods and bestowing it upon humanity. This mythological connection was chosen to symbolize the “daring” human endeavor of harnessing nuclear energy and the creation of a new element through the “fire” of a nuclear reactor.
Five Quick Facts About Promethium
- Atomic Number 61: Promethium has 61 protons in the nucleus of each of its atoms, defining its elemental identity.
- Rare Earth Element: It belongs to the lanthanide series, a group of metallic elements known for their similar chemical properties and historical classification as “rare earths.”
- Highly Radioactive: All known isotopes of promethium are radioactive, with no stable forms existing. The most stable isotope, promethium-145, possesses a half-life of approximately 17.7 years.
- Luminous Paint Component: Historically, promethium-147 has been utilized in specialized luminous paints for applications such as watch dials, clocks, and signaling devices, allowing them to glow without an external light source, similar to other radioactive luminescent materials used globally.
- Atomic Batteries: Due to its beta-particle emission, promethium-147 has been employed in miniature atomic batteries, also known as betavoltaic devices. These batteries provided long-lasting, low-power energy sources for certain specialized equipment, including some early cardiac pacemakers.