Protactinium
Protactinium is a chemical element with the symbol Pa and atomic number 91. It is a dense, silvery-gray metal which readily reacts with oxygen, water vapor, and inorganic acids. Protactinium is a member of the actinide series, located in period 7 of the periodic table, between thorium and uranium. Here are some key aspects of protactinium:
- Physical Properties: Protactinium is a dense and hard metal. It has a bright metallic luster that it retains for some time in air.
- Chemical Properties:
- Reactivity: Protactinium is highly reactive with oxygen and moisture and forms an oxide layer when exposed to air. It also reacts with most non-metallic elements and their compounds at elevated temperatures.
- Radioactivity: Protactinium is radioactive. Its most stable isotope, protactinium-231, has a half-life of about 32,760 years.
- Occurrence: Protactinium is a rare element and is found in minute quantities in uranium ores, such as pitchblende and carnotite. It is one of the rarest and most expensive naturally occurring elements.
- Production: Protactinium is usually extracted from spent nuclear fuel, which is a complex and expensive process. It can also be produced by bombarding thorium with neutrons.
- Applications:
- Scientific Research: Due to its scarcity, high radioactivity, and toxicity, protactinium has few applications and is primarily used for scientific research.
- Radiometric Dating: The isotope protactinium-231 is used in the radiometric dating of marine sediments.
- Health and Safety: Protactinium is both toxic and highly radioactive, necessitating special precautions in handling and storage. It poses a significant radiological hazard and requires appropriate containment and safety measures.
- Discovery: Protactinium was first identified in 1913 by Kasimir Fajans and O.H. Göhring and was named "proto-actinium," indicating that it is a precursor to actinium. The name was later shortened to protactinium.
Protactinium's rarity, radioactivity, and position in the actinide series make it an element of interest primarily in scientific research, particularly in the study of nuclear physics and chemistry.