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== Summary == The plum pudding model of the atom — negative charges (electrons) embedded in a larger structure of positive charge — disproved by Ernest Rutherford's gold foil experiment in 1911. Created by User:Fastfission in Illustrator
The plum pudding model was the first scientific model of the atom to describe an internal structure. It was first proposed by J. J. Thomson in 1904 following his discovery of the electron in 1897, and was rendered obsolete by Ernest Rutherford 's discovery of the atomic nucleus in 1911.
English: A simple diagram illustrating the Geiger-Marsden experiment. The left side shows the Thomson scattering pattern that the experimenters expected to see, given the plum pudding model of the atom. The right side shows the actual results, with Rutherford's new planetary model.
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English: This diagram was created for the plum pudding model article. It shows a beta particle being deflected by the atomic electrons. It shows a beta particle being deflected by the atomic electrons.
English: Created specifically for use in the plum pudding model article. Illustrates the component of the deflection caused by the atom's electrons. Illustrates the component of the deflection caused by the atom's electrons.
It became clear from his analysis in 1911 that the plum pudding model could not explain atomic structure. In 1913, Rutherford's post-doctoral student, Niels Bohr , proposed a new model of the atom, wherein electrons orbited the nucleus with classical periods, but were permitted to have only discrete values of angular momentum, quantized in ...
Top: Expected results: alpha particles passing through the plum pudding model of the atom undisturbed. Bottom: Observed results: a small portion of the particles were deflected, indicating a small, concentrated charge. Diagram is not to scale; in reality the nucleus is vastly smaller than the electron shell.