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was a central figure in the development of the atomic theory of the universe. He theorized that all material bodies are made up of indivisibly small “atoms.” Aristotle famously rejected atomism in On Generation and Corruption.
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Thomson's experiments with cathode-ray tubes showed that all atoms contain tiny negatively charged subatomic particles or electrons. Thomson proposed the plum pudding model of the atom, which had negatively-charged electrons embedded within a positively-charged "soup."
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she deduced that radioactivity does not depend on how atoms are arranged into molecules, but rather that it originates within the atoms themselves. This discovery is perhaps her most important scientific contribution.
