JOSEPH JOHN THOMSON
Joseph John Thomson was born in 1856 in Cheetham Hill near Manchester. He studied natural sciences in Manchaster. After studies he removed to Cambridge where he became Rayleigh's assistant. After Rayleigh left, Thomson, at the age of 28, took over the management of Experimental Physics Department and also of Cavendish Laboratory. He lectured as well at the universities in Princetown and in New Haven (Yale University) in United States.
His main attainment was the calculation of the value of the proportion between the charge and the mass of the particles of cathode radiation. And the next one was the discovery that cathode rays consisted of particles which he called electrons; this hypothesis he presented on the 30-th of April 1897. This discovery made physics to leave the idea of indivisibility of atom. For Thomson atom was a charged ball in which electrons were placed (the "plum cake" model). The model was good as the explanation of many physical and chemical occurrences- electrolysis, electron emission.
He also discovered that in substances he researched the number of electrons in the atoms is equal to the half of the mass number. He also researched and analysed the beams of positive ions; the beams rised near to the cathode, in the tube similar to the one due to which he discovered electrons.
In the year 1913 with Francise Aston he discovered the subsistence of stable isotopes of neon.
In the year 1915 Thomson became the chairman of the Royal Society. He held that office till year 1920 when he gave up scientific life.
He died on the 30-th of August 1940.
The experimental discovery of electron
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The elementary charge evaluations