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Francium Becomes the Last Naturally Occurring Element to be Discovered

Updated: Jul 21, 2023

#16 Science in History

07 January 1939


On this day in 1939, French scientist Marguerite Perey reveals, in an entry made in her notebook, a new, naturally occurring element – francium.

Named after France, francium is an extremely rare and highly radioactive alkali metal, with no stable isotopes. Mendeleev had anticipated its discovery, naming it ‘eka-caesium’. Marguerite Perey gave it the name ‘francium’.


Perey had originally been a technician to Marie Curie towards the end of the 1920s, Working at the Curie Institute in Paris, she discovered francium while studying the properties of actinium, a radioactive element in the actinide series.


She was able to isolate francium by bombarding a sample of actinium with protons, which produced an isotope of francium that decayed into astatine. After several years of work, Perey was able to confirm the existence of francium and describe its properties.


Francium is still not well understood due to its extreme rarity and radioactivity. It is only found in trace amounts in the earth's crust, and even then, it decays rapidly into other elements. As a result, it is extremely difficult to study and has only been produced in small quantities for research purposes.





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