J.J. Thomson

Sir Joseph John Thomson (English: Sir Joseph John Thomson, December 18, 1856 - August 30, 1940), British physicist, Nobel Prize winner in physics. He discovered the electron and determined its mass-to-charge ratio. This was the first subatomic particle discovered. In 1897, Thomson showed that cathode rays consisted of previously unknown negatively charged particles (now called electrons), which he calculated must be much smaller than atoms and have a very small mass-to-charge ratio. Thomson also discovered the first evidence of stable (non-radioactive) isotopes of elements in 1913, one of the results of his exploration of anode rays (positive ions). His experiments with Francis Aston to determine the properties of positively charged particles were the first use of mass spectrometry, leading to the development of the mass spectrometer. Thomson was awarded the 1906 Nobel Prize in Physics for his work on the conduction of electricity in gases.