Thorium is a weakly radioactive metallic chemical element, named after Thor, the Norse god of thunder.
Core Principles & Analysis
Jons Jacob Berzelius discovered thorium in 1829 in a Norwegian mineral and named it after Thor, the Norse god of thunder, decades before radioactivity was known to exist.
Thorium-232's half-life of about 14 billion years exceeds the age of the universe, so nearly all primordial thorium survives, leaving it roughly three times as abundant as uranium in Earth's crust.
Though not fissile itself, thorium-232 breeds fissile uranium-233 when it captures a neutron, the basis of thorium fuel cycles pursued in India and in molten-salt reactor research.