QUICK REFERENCE
- Symbol: U
- Atomic Number: 92
- Atomic Weight: 238.02891
- Element Classification: Actinide
- Discovered By: Martin Heinrich Klaproth
- Discovery Date: 1789
- Name Origin: Named after the planet Uranus, which had been discovered eight years earlier by William Herschel
- Density(g/cc): 19.1
- Melting Point: 1135°C
- Boiling Point: 4131°C
- Appearance: Silvery-gray metallic; it tarnishes to a dark gray in air
- Atomic Radius(pm): 175
Discovery
Uranium was discovered in 1789 by the German chemist Martin Heinrich Klaproth while he was analyzing mineral samples from the Joachimsthal silver mines in Bohemia. He isolated an oxide of a new element, which he named uranium in honor of the recently discovered planet Uranus. It wasn’t until 1841 that uranium was isolated in its metallic form by French chemist Eugène-Melchior Péligot, who reduced uranium tetrachloride with potassium.
Relation to Other Elements
Uranium is a member of the actinide series, characterized by its radioactive properties and actinide electron configuration. It is the heaviest naturally occurring element that can be found in appreciable amounts in the Earth’s crust. Uranium has several isotopes, with uranium-238 being the most abundant (99.3%), followed by uranium-235 (0.7%), which is fissile and can sustain a nuclear chain reaction.
Natural Occurrence
Uranium is found in various minerals such as uraninite (formerly pitchblende), carnotite, and autunite, and in phosphate rocks, coal, and certain granites. It is more plentiful than tin, about as common as molybdenum or arsenic, and four times more abundant than mercury. Uranium mining is a significant industry, with major producers including Kazakhstan, Canada, and Australia.
Uses
Uranium’s primary application is in the energy sector and defense:
- Nuclear Power: Uranium-235 is used as fuel in nuclear reactors to produce electricity. Through a process called nuclear fission, uranium atoms are split to release a tremendous amount of heat, which is then used to generate steam and drive turbines.
- Nuclear Weapons: Uranium-235 and uranium-233 (bred from thorium) are used in the manufacture of nuclear weapons due to their ability to sustain a rapid chain reaction.
- Depleted Uranium: The by-product of enriching uranium-235 is depleted uranium (DU), which has a lower concentration of uranium-235 than natural uranium. DU is dense and can self-sharpen upon impact, making it useful in military armor and armor-piercing projectiles.
- Radioisotope Thermoelectric Generators: Uranium-238 decays to plutonium-238, which is used in radioisotope thermoelectric generators (RTGs) for spacecraft, providing a reliable and long-lasting source of electricity.
The discovery of uranium has had profound implications for both civilian energy production and military applications. Its role in nuclear power and weapons has made uranium a critical, yet controversial, element in modern society, with significant focus on its safe handling, environmental impact, and non-proliferation.