CHAPTER 7 Atomic Structure The Subatomic ParticlesElectron:Experiments done by J.J. Thomson on cathode rays (rays emitted from metal surface when a high voltage difference is applied between two electrodes) revealed the existence of the electrons (electrically charged particles that carry electric current). Thomson's ExperimentBy measuring the amount of deflection produced by electric and magnetic fields, Thomson was able to calculate the ratioof the charge over the mass of the electron. ( Note: text uses mass/charge ratio ) C = coulomb (the SI unit for electric charge) (negative because of the charge of the particle) -1.76 x 108g C e me=Robert Millikan:(1909)By measuring the charges on oil drops sprayed through an atomizer, he was able to calculate the charge on the electron. charge on the electron: e = -1.60 x 10-19C Using the result of Thomson's Experiment Millikan was able to calculate the mass of the electron. mass of the electron: e/me= -1.76 x 108C/g-1.60 x 10-19C/me= -1.76 x 108C/gme= = 9.09 x 10-28g(very small)The mass of the electron was calculated to be smaller than the mass of the lightest element which was then known (hydrogen). Therefore, the electron should be a subatomic particle.-1.60 x 10-19C-1.76 x 108C/g1
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