Final answer:
Ernest Rutherford's alpha-particle scattering experiment led him to conclude that the nucleus of an atom contains a dense center of positive charge.
Step-by-step explanation:
The scientist whose alpha-particle scattering experiment led him to conclude that the nucleus of an atom contains a dense center of positive charge is Ernest Rutherford. Rutherford conducted an experiment where he bombarded a thin piece of gold foil with high-speed, positively charged alpha particles. Most of the alpha particles passed through the gold foil, but a small fraction were deflected, indicating the presence of a small, dense, positively charged nucleus within the atom. This experiment provided evidence for the existence of the atomic nucleus and contributed to the development of the modern model of the atom.