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Questioning
In the late 19th and 20th centuries, the concept that the atom was indivisible began to be questioned. -
Discovery of the Electron
Sir Humphry Davy and Michael Faraday used electricity to decompose chemical bounds. From the Greek "elektron". -
Cathode Rays
Phenomenon first discovered by Julius Plücker -
Ratio of Charge of an Electron
J.J. Thomson determined the ratio of the charge of an electron (e) to its mass (m) in 1897 by experimenting with deflection of cathode rays in electric and magnetic fields. -
Discovery of the Proton
Wilhelm Wien and J.J. Thomson discovered it with help of Eugen Goldstein. -
Electron's Mass
Robert Millikan performed an experiment in which he used x-rays, he determined the electron's charge, which in turn allowed the electron's mass to be calculated. -
The Nucleus
Discovered by Ernest Rutherford and coworkers. -
Discovery of the Neutron
Sir James Chadwicj conclusively demonstrate the existence of this particle. He also determine the mass of the neutron to be 1.675x10^-24g.