Historically, J.J. Thomson proposed the 'plum pudding' model of the atom, which suggested that negatively charged electrons were embedded within a diffuse sphere of uniform positive charge. To test this model, Hans Geiger and Ernest Marsden, guided by Ernest Rutherford, directed a beam of positively charged alpha particles at an extremely thin sheet of gold foil.
Under the 'plum pudding' model, the electric field within the atom was expected to be too weak to affect the fast-moving, massive alpha particles. Consequently, scientists predicted that all the alpha particles would pass straight through the foil with practically zero deflection.
The experimental results, however, showed that while almost all alpha particles went straight through, about 1 in every 8,000 8,000\,8,000 particles was deflected by very large angles (greater than 90∘90^\circ90∘). These rare, anomalous results led to a brand new understanding of atomic structure.
State the prediction regarding the path of the alpha particles based on the plum pudding model.
State what is meant by an anomalous result in a scientific experiment.
Suggest one way that scientists should address anomalous results when they occur in an experiment.
Explain how these anomalous, large-angle deflections of alpha particles led to the conclusion that the positive charge in an atom is concentrated in a small central nucleus.
Suggest two reasons why performing experimental trials is essential for the advancement of physics.
