Which of these discoveries contradict components of Dalton’s atomic theory? Check all of the boxes that apply.

Dalton’s theory treated atoms as indivisible, so the discovery of protons, neutrons, and electrons contradicts it (A). It also said all atoms of an element were identical; isotopes with different numbers of neutrons show that is not true (C). Finally, Dalton held that atoms could not change into atoms of another element, but nuclear reactions can do so (D).

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