Sir Joseph John "J. J." Thomson, OM, FRS (18 December 1856 - 30 August 1940) was a British physicist and Nobel laureate. He is credited for the discovery of the electron and of isotopes, and the invention of the mass spectrometer. Thomson was awarded the 1906 Nobel Prize in Physics for the discovery of the electron and for his work on the conduction of electricity in gases. (wikipedia)

See Also

Chronology
Keely Chronology
Quantum Chronology
Thomsonian corpuscle