Sonia Cotelle determined the half-life of thorium-230 and established the atomic number of polonium

19 June 1896, Warsaw (Poland) – 18 January 1945, Paris (France)

She graduated in general, biological, and applied chemistry from the Sorbonne University (France). She specialised in radioactive sources and, in 1919, began her work as a researcher, joining the team of scientist Marie Curie at the Institut du Radium (now the Curie Museum) in Paris (France), where she became head of the measurement department between 1924 and 1926.

Between 1926 and 1927, she worked as a chemical scientist in the Faculty of Sciences and researched polonium and actinium in collaboration with Marie Curie. She also determined the half-life or average lifetime of ionium, the name by which thorium-230 was known at the time.

Between 1927 and 1936, Cotelle lived in Czechoslovakia and determined the atomic number of polonium by X-ray spectroscopy. At the end of this period, she returned to Paris, where she continued collaborating with pioneering teams in researching radioactive elements and compounds.

She died as a result of several illnesses caused by the accidental ingestion of polonium while working in the laboratory in 1927.