According to the nuclear model of an atom,where is the whole mass of the atom located?

$A$ beam of fast-moving alpha particles was directed towards a thin gold foil. The parts $A, B$,and $C$ of the incident beam and their corresponding transmitted or reflected parts $A^{\prime}, B^{\prime}$,and $C^{\prime}$ are shown in the adjoining diagram. The number of alpha particles in:

$\sqrt{d_{1}}$ and $\sqrt{d_{2}}$ are the impact parameters corresponding to scattering angles $60^{\circ}$ and $90^{\circ}$ respectively,when an $\alpha$-particle is approaching a gold nucleus. For $d_{1} = x d_{2}$,the value of $x$ will be . . . . . .

Explain Rutherford's explanation for scattered $\alpha$-particles.

Using Thomson's model of the atom,consider an atom consisting of two electrons,each of charge $-e$,embedded in a sphere of charge $+2e$ and radius $R$. In equilibrium,each electron is at a distance $d$ from the center of the atom. What is the equilibrium separation between the electrons?

In a Geiger-Marsden experiment,what is the distance of closest approach to the nucleus of a $7.7 \;MeV$ $\alpha$-particle before it comes momentarily to rest and reverses its direction?