Final answer:
Dalton's Atomic Theory was disproved by J.J. Thomson's experiment, as it showed that atoms can be broken apart into smaller subunits or subatomic particles such as electrons, protons, and neutrons.
Step-by-step explanation:
Dalton's Atomic Theory explained a lot about matter, chemicals, and chemical reactions. Nevertheless, it was not entirely accurate, because contrary to what Dalton believed, atoms can, in fact, be broken apart into smaller subunits or subatomic particles. We have been talking about the electron in great detail, but there are two other particles of interest to us: protons and neutrons.