Francis William Aston

Francis William Aston was a British chemist and physicist who developed the mass spectrograph, identified many isotopes, and received the 1922 Nobel Prize in Chemistry.

Isotope: An isotope is a form of an element whose atoms have the same proton number but different neutron numbers. Isotopes were the distinct atomic forms Aston separated and identified.
Mass spectrograph: A mass spectrograph separates ions by mass-to-charge ratio and records their positions on a photographic plate. Aston refined this instrument to distinguish isotopes by their different trajectories.
Cavendish Laboratory: The Cavendish Laboratory is a physics research laboratory at the University of Cambridge. Aston conducted his major isotope research there under J. J. Thomson.
Whole-number rule: The whole-number rule states that isotope masses are approximately whole-number multiples of hydrogen’s atomic mass. Aston’s measurements revealed a useful pattern in isotope masses.
Aston mass spectrograph: The Aston mass spectrograph is a mass spectrograph designed by Francis William Aston for precise isotope analysis. This instrument produced the measurements behind many of Aston’s isotope discoveries.
Mass spectrometry: Mass spectrometry measures ions by their mass-to-charge ratios to identify or quantify substances. Aston’s instrument established the foundations of this measurement technique.
Electromagnetic separation: Electromagnetic separation sorts charged particles by their responses to electric and magnetic fields. Aston’s instrument used these fields to spread ions into separate paths.
J. J. Thomson: J. J. Thomson was a British physicist who discovered the electron and studied positive rays. Thomson’s positive-ray apparatus and mentorship shaped Aston’s early research.
Mass defect: Mass defect is the difference between a nucleus’s mass and the summed masses of its separate protons and neutrons. Aston’s precise masses revealed departures from simple whole-number atomic weights.
Neon isotopes: Neon isotopes are atoms of neon with different numbers of neutrons, chiefly neon-20 and neon-22 in natural samples. Aston’s early mass-spectrograph results showed that neon contained atoms of different masses.

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