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Wednesday, December 18, 2013

CHEMISTRY BASICS PART 1 : JOSEPH JOHN THOMSON AND AN ATOM

I decided to do the Chemistry basics posts in full details. So,I'll be doing one event per day unless it is completed. Today I'm going to explain the concept of an atom as proposed by J J Thomson. (I have a chemistry test today!) Thomson is the scientist who's credited with the discovery of electrons. He was the first one who proposed that atoms are spherical in shape and that electrons are embedded in this spherical body. He explained the model of an atom as that of a Christmas Pudding and that electrons where embedded in it like dry fruits.



Thomson, in 1897, was the first to suggest that the fundamental unit was over 1000 times smaller than an atom, suggesting the subatomic particles now known as electrons. Thomson discovered this through his explorations on the properties of cathode rays Thomson made his suggestion on 30 April 1897 following his discovery that Lenard Rays could travel much further through air than expected for an atom-sized particle. He estimated the mass of cathode rays by measuring the heat generated when the rays hit a thermal junction and comparing this with the magnetic deflection of the rays. His experiments suggested not only that cathode rays were over 1000 times lighter than the hydrogen atom, but also that their mass was the same whatever type of atom they came from. He concluded that the rays were composed of very light, negatively charged particles which were a universal building block of atoms. He called the particles "corpuscles", but later scientists preferred the name electron which had been suggested by George Johnston Stoney in 1891, prior to Thomson's actual discovery.
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