Question

What would make a heavy, positive alpha particle bounce back like that?

A. The alpha particle collided with an electron.
B. The alpha particle collided with some negatively charged particle.
C. The alpha particle collided with an object of weak positive charge.
D. The alpha particle collided with an object of dense positive charge.
E. The alpha particle was attracted to the electrons in the atom.

Answer 1

The heavy, positive alpha particles in Rutherford's gold foil experiment were bounced back due to a collision with the dense, positively charged gold nucleus, affirming the existence of a small, compact nucleus within atoms.

Step-by-step explanation:

In the context of Rutherford's gold foil experiment, heavy, positive alpha particles being deflected and sometimes even bouncing back indicates that they collided with something dense and positively charged. The correct answer is that the alpha particle collided with an object of dense positive charge: the gold nucleus. This result was unexpected according to Thomson's model of the atom, which proposed atoms were composed of diffuse positive and negative charges. Instead, the experiment revealed that atoms have a very small, dense nucleus with a positive charge that repels the positively charged alpha particles in a way similar to how a cue ball is scattered when it hits another billiard ball with the same charge. As per Coulomb's law, like charges repel, and the intense scattering of the alpha particles indicated a forceful repulsion from the dense, positively charged gold nuclei. Therefore, option D is correct.