Atomic Properties of U
- Atomic Number of U
- 92
- Atomic Mass of U
- 238.0300 u
- Electron Configuration
- [Rn] 5f3 6d1 7s2
- Electronegativity
- 1.38
- Block
- f-block
- Group
- —
- Period
- 7
Martin Heinrich Klaproth identified uranium in pitchblende in 1789 and named it for the recently discovered planet Uranus. Eugène-Melchior Péligot isolated the metal decades later. Long before nuclear fission was understood, uranium compounds colored glass and ceramics, often producing yellow or green fluorescence under ultraviolet light. The metal itself is silvery, not naturally “pale green.”
Natural uranium is mostly uranium-238, with about 0.7 percent uranium-235 and traces of uranium-234. Uranium-235 can sustain a neutron chain reaction and powers reactors that light cities after fuel preparation and controlled fission. Uranium-238 can breed plutonium-239 in reactors and also begins a long natural decay series. Ratios involving uranium and lead provide major clocks for dating rocks.
The same nuclear physics entered weapons history, including the uranium weapon used on Hiroshima in 1945. Civilian electricity and weapons are not interchangeable uses, but they share fuel-cycle, safeguards, waste, and proliferation responsibilities that cannot be reduced to a heroic or villainous personality.
Uranium is chemically toxic as a heavy metal and radioactive, with risk depending on isotope, chemical form, route, and duration of exposure. Mining, processing, fuel use, and waste storage require different controls.
This Corebound history keeper does not offer one moral. It offers a demand for precision: distinguish isotopes, distinguish compounds from metal, distinguish a controlled reactor from a weapon, and remember the people and environments affected across the entire material cycle.