September 1, 1877 – Birth of Francis William Aston, inventor of the mass spectrometer and discoverer of isotopes

In 1909, at the invitation of Joseph John Thomson (discoverer of the electron), he began working at the Cavendish Laboratory at Cambridge University, identifying neon isotopes and investigating electrical discharges in low-pressure tubes.

After World War I, in 1919, he invented the mass spectrometer. An experimental device for separating charged particles according to their mass.

In his early investigations with the mass spectrograph, Aston discovered that when he passed a sample of pure neon gas through the instrument, two separate spots formed on the detector, which meant that the gas contained atoms corresponding to two different masses. He, therefore, interpreted his discovery as indicating the existence of two different types of neon atoms, and that both must have the same number of protons since all forms of neon always contain the same number of protons, but a different number of neutrons. As a consequence, their atomic masses must be different. With this discovery, Aston provided the first experimental proof of the existence of isotopes.

He continued to conduct experiments and succeeded in identifying 212 of the 287 isotopes of non-radioactive elements in the periodic table. This led him to join the Royal Society in 1921 and to receive the Nobel Prize in Chemistry in 1922.

If you want to know more about this scientist, click on the following link: Francis William Aston