Final answer:
Ernest Rutherford conducted the gold foil experiment, which showed that atoms have a dense, positively-charged nucleus, disproving the plum pudding model.
Step-by-step explanation:
The developer of modern atomic theory who conducted the famous gold foil experiment is Ernest Rutherford. In this experiment, Rutherford and his colleagues, Hans Geiger and Ernest Marsden, aimed alpha particles at a very thin sheet of gold foil. Most of the particles passed straight through, but a few were deflected at significant angles, and some even reflected back to the source. This result was contrary to the then-accepted plum pudding model and led to the conclusion that atoms have a very small, dense, positively-charged nucleus at their center. Therefore, the correct answer to the question is (b) Ernest Rutherford.