Rutherford's experiment, in which he fired alpha particles of 7.7 MeV kinetic energy at a thin gold foil, showed that nuclei were very much smaller than the size of an atom because A) some alpha particles passed through the foil undeflected. B) some alpha particles were deflected backwards. C) some alpha particles were captured by the gold nuclei. D) the alpha particles could not get closer than 10−¹⁰ m to the gold nuclei. E) the alpha particles split into deuterium nuclei when they encountered the gold nuclei.

Question

Quizplus · Accepted Answer

The fact that some alpha particles were deflected backwards suggests that they had encountered a small, positively charged nucleus, which caused a significant change in their direction. This can only happen if the size of the nucleus is much smaller than the size of the atom as a whole.

Rutherford's Experiment, in Which He Fired Alpha Particles of 7