Francis William Aston
Born: 1 September 1877, Harborne, United Kingdom
Died: 20 November 1945, Cambridge, United Kingdom
Affiliation at the time of the award: University of Cambridge, Cambridge, United Kingdom
Prize motivation: "for his discovery, by means of his mass spectrograph, of isotopes, in a large number of non-radioactive elements, and for his enunciation of the whole-number rule."
Prize share: 1/1
After it became clear that elements could have different isotopes, i.e., occur in different variants with different atomic weights, Francis Aston developed the mass spectrograph in 1919 to map the different isotopes. In the mass spectrograph, beams of atoms were generated in a tube with the aid of an electrical field. When the beams passed through an electrical and magnetic field, the lighter isotopes were bent more than the heavier ones. Aston came to the conclusion that the weight of the isotopes was very close to whole-number multiples of a unit.