A white radioactive metallic element belonging to the actinoids; a.n. 92; r.a.m. 238.03; r.d. 19.05 (20°C); m.p. 1132±1°C; b.p. 3818°C. It occurs as uraninite, from which the metal is extracted by an ion-exchange process. Three isotopes are found in nature: uranium-238 (99.28%), uranium-235 (0.71%), and uranium-234 (0.006%). As uranium-235 undergoes nuclear fission with slow neutrons it is the fuel used in nuclear reactors and nuclear weapons; uranium has therefore assumed enormous technical and political importance since their invention. It was discovered by Martin Klaproth (1747–1817) in 1789.

https://www.webelements.com/uranium/ Information from the WebElements site