Final answer:
J. J. Thomson discovered the electron in 1897 and proposed significant advancements in understanding atomic structure.
Explanation:
J. J. Thomson is credited with the discovery of the electron in 1897 through his experiments studying cathode rays, proposing that they were unique particles later named electrons. Thomson's work led to the understanding of the presence of electrons in atoms, contributing to the development of atomic models such as the plum pudding model and paving the way for further research in atomic structure.
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