Choose the correct options and explain the reason for the correct and incorrect options in the context of Ernest Rutherford’s gold foil experiment:
The experiment clearly showed the existence of neutrons in the nucleus.
False. The experiment concluded that most of the mass of an atom is concentrated in a small region at the centre called the nucleus, but it did not clearly show the existence of neutrons in the nucleus.
The results disproved the plum pudding model and led to the idea of a nucleus at the centre of the atom.
True. Thomson’s model failed to explain the results of the gold foil experiment, particularly the large-angle deflections of some α-particles. This disproved the plum pudding model and led to the idea of a nucleus at the centre of the atom.
The large deflection of a few alpha particles indicated that most of the mass of the atom and positive charge are packed into a tiny centre.
True. The large deflection and bouncing back of a few alpha particles indicated that most of the mass of an atom is concentrated in a small region at the centre called the nucleus. Since alpha particles are positively charged, this tiny centre must also contain the positive charge to cause such sharp deflections.
The way alpha particles were deflected showed that electrons move around the nucleus.
False. The deflection of alpha particles showed the existence of a tiny, positively charged nucleus at the centre, but it did not show that electrons move around the nucleus.
Explanation
Option (i) is incorrect because Rutherford's experiment established the existence of the nucleus as a small, dense region of mass and positive charge, not the existence of neutrons. Option (ii) is correct because the observed large-angle deflections contradicted Thomson's model of evenly spread positive charge, disproving the plum pudding model and establishing the nuclear model. Option (iii) is correct because the sharp deflection and bouncing back of a few alpha particles proved that both mass and positive charge are concentrated in a tiny central nucleus. Option (iv) is incorrect because the scattering of alpha particles only provided evidence for the nucleus; it did not demonstrate the movement of electrons around it.