Rutherford's gold foil experiment

1911

At Manchester, Ernest Rutherford's students fired alpha particles at thin gold foil. Most went straight through, but a few bounced wildly back. It was, Rutherford said, as if you fired artillery at tissue paper and it came back at you. He concluded that atoms had tiny, dense, positively charged nuclei surrounded by mostly empty space. The plum pudding model was dead. Modern atomic physics had its foundation.