Unlocking the Atom: Three Experiments That Revealed Its Structure

Fundamental Discoveries in Atomic Structure The road toward the modern atomic model began in 1897 with the discovery of the electron—the first identified sub‑atomic particle—by J. J. Thomson. In 1909, Robert Millikan took the next crucial step by quantifying a fundamental property of that particle, precisely measuring the elementary electric charge. This knowledge was then revolutionized by Ernest Rutherford’s experiment, which knocked down Thomson’s “plum‑pudding” model by demonstrating the existence of a dense, positively charged atomic nucleus, thereby establishing the nuclear model of the atom.