1898
Marie and Pierre Curie discovered the radioactive elements radium and polonium.
Before this discovery, uranium and thorium were the only known radioactive
elements. While studying uranium minerals. Marie Curie noticed two minerals
were much more radioactive than uranium itself. She and her husband, Pierre,
chemically separated the compounds in the minerals and found a substance 400
times more radioactive than uranium. Marie named this substance polonium, after
her native country of Poland. The Curies also found one of the uranium minerals
contained another element more radioactive than uranium. They named this
element radium. The Curies won the 1903 Nobel Prize in physics for these
discoveries.
Marie Curie won the Nobel Prize in chemistry in 1910 for obtaining elemental
radium in the metallic state. She was the first person to win the Nobel Prize
twice.
Soon after the Curies' discoveries, other scientists discovered the radioactive
element actinium. By 1912, thirty radioactive elements had been discovered.
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