(N/A) Rutherford performed an experiment by bombarding a very thin gold foil with high-energy $\alpha$-particles. The observations were as follows:
$(i)$ Most of the fast-moving $\alpha$-particles passed straight through the gold foil without any deflection.
$(ii)$ Some of the $\alpha$-particles were deflected by the foil by small angles.
$(iii)$ Out of every $12000$ particles,one appeared to rebound (deflected by $180^{\circ}$).
Based on these observations,the following conclusions were drawn:
$(i)$ There is a positively charged center in an atom called the nucleus. Nearly all the mass of an atom resides in the nucleus.
$(ii)$ The electrons revolve around the nucleus in well-defined circular orbits.
$(iii)$ The size of the nucleus is very small compared to the total size of the atom.