a soft silvery-white tetravalent radioactive metallic element; isotope 232 is used as a power source in nuclear reactors; occurs in thorite and in monazite sands
A chemical element (symbol Th) with atomic number 90: a weakly radioactive, malleable, moderately hard silvery metal that tarnishes black when exposed to air.
The name thorium comes from the Norse god Thor combined with the chemical suffix -ium. It was named to honor the deity associated with thunder and lightning.