Thorium oxide was discovered in 1828 by the Swedish chemist Jon Jakob Berzelius (1779-1848), who is called "The Father of Modern Chemistry."  In 1828, Berzelius was given a mineral by the Reverend Has Morten Thrane Esmark. After determining that it was a new element, Berzelius named his   discovery after the Norse God of thunder and weather, Thor.

Read one of the first articles published about the radioactive nature of Thorium.  Lord Rutherford of Nelson in Philosophical Magazine, 1900, "A Radioactive Substance emitted from Thorium Compounds."

Lord Rutherford "found that thorium compounds continuously emit radioactive particles of some kind, which retain their radioactive powers for several minutes."

Lord Rutherford noted " another anomally that thorium compounds exhibit is the ease with which the radiation apparently passes through paper."