Symbol: Th
Atomic number: 90
Atomic weight: 232.038
Grey radioactive metallic element. Belongs to actinoids. Found in monazite sand in Brazil, India and the US. Thorium-232 has a half-life of 1.39x10^10 years. Can be used as a nuclear fuel for breeder reactors. Thorium-232 captures slow neutrons and breeds uranium-233. Discovered by Jons J. Berzelius in 1829.