What is the dimension of an atom?

Discuss the experimental results of Geiger-Marsden's $\alpha$-particle scattering.

$A$ beam of fast-moving alpha particles was directed towards a thin gold foil. The parts $A'$,$B'$,and $C'$ of the transmitted and reflected beams corresponding to the incident parts $A$,$B$,and $C$ of the beam are shown in the adjoining diagram. The number of alpha particles in:

According to classical theory,the Rutherford atom was:

If an alpha particle with energy $7.7 \text{ MeV}$ is bombarded on a thin gold foil, the closest distance from the nucleus it can reach is . . . . . . $\text{m}$. (Atomic number of gold $= 79$ and $\frac{1}{4 \pi \epsilon_0} = 9 \times 10^9$ in $SI$ units)

State the limitations of the plum pudding model of the atom.