J. J. Thomson

Sir Joseph John Thomson OM PRS (18 December 1856 – August 30, 1940) was an English physicist and Nobel Laureate in Physics, credited with the discovery and identification of the electron, the first subatomic particle to be discovered.

In 1897, Thomson shows that cathode rays are composed of previously unknown negatively charged particles (now called electrons), which he calculatea must have bodies much smaller than atoms and a very large charge-to-mass ratio.

Thomson is also credited with finding the first evidence for isotopes of a stable (non-radioactive) element in 1913, as part of his exploration into the composition of canal rays (positive ions).

His experiments to determine the nature of positively charged particles, with Francis William Aston, are the first use of mass spectrometry and lead to the development of the mass spectrograph.

Thomson is awarded the 1906 Nobel Prize in Physics for his work on the conduction of electricity in gases

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