<P> The physicist J.J. Thomson measured the mass of cathode rays , showing they were made of particles , but were around 1800 times lighter than the lightest atom , hydrogen . Therefore , they were not atoms , but a new particle , the first subatomic particle to be discovered , which he originally called `` corpuscle '' but was later named electron , after particles postulated by George Johnstone Stoney in 1874 . He also showed they were identical to particles given off by photoelectric and radioactive materials . It was quickly recognized that they are the particles that carry electric currents in metal wires , and carry the negative electric charge within atoms . Thomson was given the 1906 Nobel Prize in Physics for this work . Thus he overturned the belief that atoms are the indivisible , ultimate particles of matter . Thomson also incorrectly postulated that the low mass , negatively charged electrons were distributed throughout the atom in a uniform sea of positive charge . This became known as the plum pudding model . </P>
<P> The physicist J.J. Thomson measured the mass of cathode rays , showing they were made of particles , but were around 1800 times lighter than the lightest atom , hydrogen . Therefore , they were not atoms , but a new particle , the first subatomic particle to be discovered , which he originally called `` corpuscle '' but was later named electron , after particles postulated by George Johnstone Stoney in 1874 . He also showed they were identical to particles given off by photoelectric and radioactive materials . It was quickly recognized that they are the particles that carry electric currents in metal wires , and carry the negative electric charge within atoms . Thomson was given the 1906 Nobel Prize in Physics for this work . Thus he overturned the belief that atoms are the indivisible , ultimate particles of matter . Thomson also incorrectly postulated that the low mass , negatively charged electrons were distributed throughout the atom in a uniform sea of positive charge . This became known as the plum pudding model . </P>
who determined the mass of the electron ( points 3 )
who determined the mass of the electron ( points 3 )
J.J. Thomson
J.J. Thomson