Protactinium
Definition and meaning of Protactinium in chemistry.
Protactinium is a rare, highly radioactive actinide element carrying the symbol Pa and atomic number 91. It is a dense, silvery gray metal that readily reacts with oxygen, water vapor, and inorganic acids. It naturally occurs in very small amounts as an intermediate decay product of uranium-235.
In more detail
Located directly between thorium and uranium on the periodic table, protactinium is an exceptionally rare and expensive element to extract from natural ores. Its most stable and abundant isotope, protactinium-231, features a half-life of roughly 32760 years and is discovered in pitchblende at minute concentrations of merely one part per million. The chemical behavior of protactinium is incredibly complex as it exhibits multiple oxidation states, typically favoring the +5 state but frequently displaying the +4 state while forming diverse complex ions in aqueous solutions. The bulk metal exhibits unique physical properties, including becoming entirely superconducting at extremely low temperatures below 1.4 Kelvin. Its profound radioactivity and high biological toxicity mandate that any analytical research involving the element must be conducted in highly specialized containment laboratories. Unlike its immediate actinide neighbors, protactinium currently lacks any large scale commercial or industrial applications outside of highly specialized academic and scientific research.
Key facts
| Field | General Chemistry |
|---|---|
| Symbol | Pa |
| Atomic number | 91 |
| Atomic mass | 231.04 u |
| Category | Actinide |
| State at room temperature | Solid |
| Melting point | 1568 degrees Celsius |
| Year discovered | 1917 |
Protactinium-231 is utilized in paleoceanography alongside thorium-230 to determine the radiometric dating of deep sea sediments.
Frequently asked questions
Why is protactinium so incredibly rare on Earth?
It exists almost exclusively as a short-lived intermediate in the decay chain of uranium-235, which itself makes up only a small fraction of natural uranium.
Are there any commercial applications for protactinium?
Because of its rarity, exorbitant cost of extraction, and intense radioactivity, it is currently used exclusively for basic scientific research.