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

If the gold nucleus was large, as was previously believed, Rutherford would have expected the alpha particles to be deflected only slightly from their original path. However, Rutherford observed that some alpha particles were deflected at very large angles, and some even bounced back directly towards the source. This led him to conclude that the atom must contain a very small, positively charged nucleus, while the majority of the atom's volume (and its electrons) were distributed around the nucleus in a diffuse cloud. Thus, the correct answer is B as the observation exactly explains how nuclei were much smaller than the size of an atom.

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