Determine the mass number (nucleon number) of the atom.
Explain why the model represents a charged atom.
The student builds a new model of another isotope of the same element. Describe the nucleus of this new model.
Americium-241 is radioactive. Its nuclide notation is $^{241}_{94}\text{Am}$. Determine the number of neutrons in a nucleus of americium-241.
A nucleus of americium-241 emits an $\alpha$-particle and decays to uranium-237. Complete the nuclear equation for the decay of americium-241: $^{241}_{94}\text{Am} \rightarrow \; \alpha + \,^{237}_{92}\text{U}$.
Geiger and Marsden investigated the structure of gold atoms. Fig. 11.1 shows one version of their apparatus. Alpha-particles hit a thin gold foil. Suggest why it is necessary to remove all the air from the container.
The alpha-particles are emitted from the source at random. Explain why most of the alpha particles from the source do not reach the gold foil.
Fig. 11.2 shows a model of a gold-foil atom, with the nucleus at the centre. The alpha-particle labelled A is deflected by the nucleus, as shown. On Fig. 11.2, complete the path of the alpha-particle labelled B.
Explain how the alpha-particle scattering experiment gives evidence for the existence of a small nucleus inside the atom.