QUICK REFERENCE
- Symbol: Pa
- Atomic Number: 91
- Atomic Weight: 231.03588
- Element Classification: Actinide
- Discovered By: Kasimir Fajans and Oswald Helmuth Göhring; independently by Frederick Soddy and John Cranston
- Discovery Date: 1913 (discovery of isotope Protactinium-234), 1917 (discovery of isotope Protactinium-231)
- Name Origin: From the Greek ‘protos’ meaning first and ‘actinium’, meaning “parent of actinium”, as it decays into actinium
- Density(g/cc): 15.37
- Melting Point: 1572°C
- Boiling Point: ~4000°C (estimated)
- Appearance: Bright, silvery metallic luster
- Atomic Radius(pm): 163
Discovery
Protactinium was discovered through the work of several scientists. In 1913, Kasimir Fajans and Oswald Helmuth Göhring discovered the isotope protactinium-234 in Germany, while Frederick Soddy and John Cranston independently discovered the same isotope in the UK. The more stable isotope, protactinium-231, was identified in 1917 by Otto Hahn and Lise Meitner in Germany, and by Frederick Soddy and John Cranston in the UK. The name “protactinium” was suggested in 1918, indicating that it is the parent of actinium, as protactinium-231 decays to actinium-227.
Relation to Other Elements
Protactinium is a member of the actinide series, characterized by its radioactive properties and filling of the 5f electron orbital. It shares similarities with other actinides, including chemical reactivity and the ability to form compounds in multiple oxidation states, most commonly +4 and +5. Protactinium’s chemistry and behavior are less studied compared to other actinides due to its scarcity, high radioactivity, and toxicity.
Natural Occurrence
Protactinium is one of the rarest and most expensive naturally occurring elements. It is found in trace amounts in uranium ores, such as uraninite, and is primarily obtained as a by-product of uranium processing. Due to its long half-life, protactinium-231 (32,760 years) contributes to the understanding of geological and environmental processes.
Uses
Due to its scarcity, radioactivity, and toxicity, protactinium has limited practical applications:
- Scientific Research: Protactinium’s primary use is in scientific research, including studies on the behavior of actinides, nuclear physics, and radiometric dating techniques for geological and environmental samples.
- Nuclear Applications: Theoretical studies have considered the use of protactinium in nuclear reactors and in the breeding of nuclear fuel, although practical applications have not been realized due to the element’s challenges.
The discovery of protactinium contributed to the development of nuclear science and our understanding of the actinide series. While its practical uses remain limited, ongoing research into actinides may reveal new applications for protactinium in the future.