In 1935, Irene Joliot-Curie won half of the Nobel Prize in Chemistry “in recognition of their synthesis of new radioactive elements.”  Irène was the elder daughter of Pierre Curie and Marie Skłodowska–Curie.

Radiation from radioactive substances also became an important tool in investigating atoms. When Irene Joliot-Curie and Frédéric Joliot bombarded a thin piece of aluminum with alpha particles (helium atom nuclei) in 1934, a new kind of radiation was discovered that left traces inside an apparatus known as a cloud chamber.

The pair discovered that the radiation from the aluminum continued even after the source of radiation was removed. This was because aluminum atoms had been converted into a radioactive isotope of phosphorus. That meant that, for the first time in history, a radioactive element had been created artificially.