CHAPTER 31 THE ATOM, RADIOACTIVITY AND NUCLEAR ENERGY CHAPTER 31
The atom, radioactivity and nuclear energy
Learning objectives By the end of this chapter, you should be able to:
outline Rutherford’s gold foil experiment and conclusions about atomic theory
use the Bohr model to explain and calculate emission spectra from atoms
distinguish between continuous and line spectra and outline how they are produced
detail the three types of radiation and their properties, with reference to experiments
understand the stages of a decay chain by calculating each radiation involved
Introduction
We have already studied the effect that electrons can have and how they are produced. In this chapter, we will look at the structure of the atom and the power that is contained within its nucleus.
Rutherford’s gold foil experiment
At the beginning of the twentieth century, it was known that the atom contained electrons and matching positive charges, but the position and size of these was still a mystery. In 1911, Ernest Rutherford performed an experiment to throw light on the actual dimensions and structure of an atom. The experiment was known as the gold foil experiment and was conducted as follows (see Fig. 31.1):
• Alpha particles (helium nuclei) were fired at extremely thin gold foil.
• The helium nuclei were positive and the thin foil was just a few atoms thick.
• Any alpha particles that hit the fluorescent screen caused a scintillation (flash).
