Answer: J. J. Thomson’s experiment disproved the theory that an atom is indivisible.
Explanation:
1) Before J.J Thomson's experiment, Dalton's atomic theory depicted the atom as an extremely tiny and indivisible particle. All the matter was formed by atoms; all the atoms of a same element were identical, and different of the aoms of other element; the atoms could not be created or destroyed; and the compounds were formed by the rearrangement of the atoms, which explained the conservation of the mass.
2) J.J Thomson's experiments with cathode rays (negatively charged particles, i.e. electrons, present in all the matter) led him to the conclusion that there were particles much smaller (lighter) than the smallest known atom (hydrogen), which meant that the atom was not indivisible.
Thomson proposed the called plum pudding model, which depicted the negatively charged electrons embeded in a uniform positive mass.
