(a(i))[1]
State the experimental observations that show radioactive decay is spontaneous.
(a(ii))[1]
State the experimental observations that show radioactive decay is random.
(b)[3]
On Fig. 7.1, fill in the charge and mass of $\alpha$-particles, $\beta$-particles and $\gamma$-radiation. Give example speeds for $\alpha$-particles and $\gamma$-radiation emitted by a laboratory source.
(c)[2]
Explain the process by which $\alpha$-particles lose energy when they pass through air.