University of Illinois at Urbana-Champaign
Rare Book Room Exhibit

Aston's invention of the mass spectrograph, an instrument giving a concentrated and extremely detailed breakdown of the constituents of analyzed material, enabled him to discover that elements are composed of atoms of varying mass, and that the atomic weight of an element is an average of the atoms comprising it. Aston used the word "isotopes" to describe atoms of differing weights within the same element, a term first coined by Frederick Soddy to describe separate elements that are nevertheless homogeneous in chemical behavior. Aston was awarded the Nobel Prize for chemistry in 1922 "for his discovery, by means of his mass spectrograph, of the isotopes of a large number of non-radioactive elements, as well as for his discovery of the whole-number rule."

Norman Library of Science, 77.

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