Curie’s Nobel lecture: radium and changing atoms

On December 11, 1911, Marie Curie delivered her Nobel lecture in Stockholm, Radium and the New Concepts in Chemistry. She explained how radioactivity led to new elements, focusing on radium’s isolation, chemical properties and evidence of atomic transformation.

She had shared the 1903 physics prize with Pierre Curie and Henri Becquerel. Her 1911 chemistry prize recognised work on polonium and radium, including the isolation of radium.

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Curie measured uranium-bearing minerals and found activity stronger than their uranium content could explain. She searched for more active substances, measuring each fraction after chemical separation to follow where the unknown component accumulated.

Polonium followed bismuth during processing, while radium accompanied barium. Activity measurements guided separation and allowed very small quantities of new elements to be followed through large amounts of material.

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Radium’s chemistry resembled barium’s, making repeated separation necessary. Curie obtained purer radium salts, measured atomic weight and used spectroscopic evidence to establish its identity. In 1910, she and André Debierne also prepared metallic radium.

Radium remained radioactive in different chemical states. The lecture connected activity with the atom itself: chemical processing changed combinations while activity followed the radium present.

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Curie discussed experiments in which radium produced helium and Rutherford and Soddy’s theory of radioactive transformations. Atoms could yield other atoms through decay, with radioactive substances passing through sequences toward more stable states.

The lecture brought separation, atomic weight, radiation and transformation together. Small amounts of radium extracted from large quantities of mineral became tools for investigating radioactivity and the structure of matter.

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