The element thorium was discovered by Jöns Jacob Berzelius in 1828. He received a sample of an unusual black mineral. This mineral contained a large number of elements and it also had another substance that Berzelius could not identify, which eventually led to the discovery of thorium.
After some analysis, he concluded that the mineral contained a new element and he called the black mineral thorite, as a tribute to the Scandinavian god Thor. Later, he confirmed that thorite was an oxide of a new element, which he named thorium.
Thorium was discovered to be radioactive by Gerhard Schmidt in 1898. After uranium, it was the first element to be identified as such. The most important discovery about thorium took place in the early 1900s when Ernest Rutherford and Frederick Soddy found that the element decayed into other elements at a fixed rate. It was a key discovery in our understanding of the radioactive elements.
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