(a)[2]
Describe the arrangement of particles in an atom of the nuclide $^{235}_{92}\text{U}$.
(b(i))[1]
The deflection of $lpha$-particles by a thin metal foil is studied using the arrangement shown in Fig. 6.1. The whole apparatus is enclosed in a vacuum. Explain why the apparatus is enclosed in a vacuum.
(b(ii))[3]
State and explain the readings recorded by D when it is moved along WXY.
(c)[3]
A beam of $lpha$-particles gives a current of $1.5\,\text{pA}$. Calculate how many $lpha$-particles per second pass a point in the beam.