THORIUM

Thorium is a weakly radioactive metallic chemical element with the symbol Th and atomic number 90. Thorium is silvery and tarnishes black when it is exposed to air, forming thorium dioxide; it is moderately hard, malleable, and has a high melting point.



Symbol: Th
Electron configuration: [Rn] 6d27s2
Atomic number: 90
Atomic mass: 232.03806 u
Discoverer: Jöns Jacob Berzelius