Uranium is a silvery-white metallic chemical element in the actinide series, weakly radioactive.
Core Principles & Analysis
Martin Heinrich Klaproth identified uranium in pitchblende in 1789 and named it after Uranus, the planet discovered eight years earlier.
Natural uranium is about 99.3% uranium-238 (half-life 4.47 billion years) and only 0.7% fissile uranium-235, which is why most reactor fuel must be isotopically enriched.
Otto Hahn and Fritz Strassmann's 1938 discovery of uranium fission, explained by Lise Meitner and Otto Frisch, launched the nuclear age, while uranium-lead dating established Earth's 4.5-billion-year age.