On the periodic table, uranium is the element named after the planet Uranus. German chemist Martin Heinrich Klaproth discovered it in 1789 and chose the name to follow the recent discovery of Uranus.
Uranium is element 92 and belongs to the actinide series. It is a heavy, weakly radioactive metal found naturally in Earth’s crust. The isotope uranium-238 is the most abundant naturally occurring uranium isotope, while uranium-235 is important because it can sustain a nuclear chain reaction.
Uranium’s planetary naming tradition continued with neptunium, element 93, named after Neptune, and plutonium, element 94, named after Pluto. These names also follow the order of the celestial bodies in the Solar System.
Klaproth did not isolate pure uranium metal; he identified uranium oxide. Pure uranium was isolated later, in 1841, by Eugène-Melchior Péligot. The discovery and later nuclear applications made uranium one of the best-known actinide elements.