Alpha particle tracks through gases and thin metal foils show few deflections. What does this tell us about the atom?

Answer 1

Large deflections require close encounters with a nucleus. Because the protons of the target material are located in nuclei that occupy a very small fraction of the atom's volume most alpha particles go though without a close encounter with a nucleus. The electron cloud around each nucleus is incapable of causing much deflection of alpha particles.

Learn more by reading about the Rutherford experiment.. one of the most important experiments in the history of science