jan 1, 1932 - James Chadwick

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Chadwick, a British chemist who lived from 1891-1974, discovered neutrons and created the modern atomic model. He discovered neutrons by realizing that atoms had mass that couldn't be accounted for by protons and electrons. His modern atomic model showed a nucleus made of neutrons and protons surrounded by a cloud of electrons that orbited the nucleus like planets.

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