what atom did j.j thomson discover?
The electron in chemistry Tendencies of recent investigations in the field of physics Electricity and matter Rays of positive electricity and their application to chemical analyses Conduction of electricity through gases The discharge of electricity through gases Elements of the mathematical theory of electricity and magnetism A treatise on the motion of vortex rings
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 That same year , J.J. Thomson conducted an experiment in which he channeled a stream of neon ions through magnetic and electric fields , striking a photographic plate at the other end . He observed two glowing patches on the plate , which suggested two different deflection trajectories . Thomson concluded this was because some of the neon ions had a different mass . The nature of this differing mass would later be explained by the discovery of neutrons in 1932 . 

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 Thomson 's plum pudding model was disproved in 1909 by one of his former students , Ernest Rutherford , who discovered that most of the mass and positive charge of an atom is concentrated in a very small fraction of its volume , which he assumed to be at the very center . 

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 The thesis was good enough , though , for Burhop to be awarded an 1851 Exhibition Scholarship to study at Cambridge University 's Cavendish Laboratory under Lord Rutherford in 1933 . The scholarship included a first @-@ class ticket to London on the liner RMS Oronsay . At this time the Cavendish Laboratory was one of the leading centres of physics in the world . In 1932 , Cavendish laboratory scientists John Cockcroft and Ernest Walton split the atomic nucleus , James Chadwick discovered the neutron , and Patrick Blackett and Giuseppe Occhialini confirmed the existence of the positron . Burhop was supervised by a fellow Australian , Mark Oliphant . He was initially assigned a task of investigating the diffusion of positive alkali metal ions on hot metal surfaces , but soon switch to a more interesting subject , the measurement of the excitation function for the pairs of deuterons producing a triton through nuclear fusion : 

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 In 1873 , another committee of the BAAS that also counted Maxwell and Thomson among its members and tasked with " the Selection and Nomenclature of Dynamical and Electrical Units " recommended using the CGS system of units . The committee also recommended the names of " dyne " and " erg " for the CGS units of force and energy . The CGS system became the basis for scientific work for the next seventy years . 

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 Even at such long odds , the danger was sufficiently great to be taken seriously . Thomson , at Imperial College London , and Mark Oliphant , an Australian physicist at the University of Birmingham , were tasked with carrying out a series of experiments on uranium . By February 1940 , Thomson 's team had failed to create a chain reaction in natural uranium , and he had decided that it was not worth pursuing . But at Birmingham , Oliphant 's team had reached a strikingly different conclusion . Oliphant had delegated the task to two German refugee scientists , Rudolf Peierls and Otto Frisch , who could not work on the University 's radar project because they were enemy aliens and therefore lacked the necessary security clearance . They calculated the critical mass of a metallic sphere of pure uranium @-@ 235 , the only fissile isotope found in significant quantity in nature , and found that instead of tons , as everyone had assumed , as little as 1 to 10 kilograms ( 2 @.@ 2 to 22 @.@ 0 lb ) would suffice , which would explode with the power of thousands of tons of dynamite . 
