Use Rutherford's gold-foil experiment to answer each of the...

Use Rutherford's gold-foil experiment to answer each of the following:
a. What did Rutherford expect to happen when he aimed particles at the gold foil?
b. How did the results differ from what he expected?
c. How did he use the results to propose a model of the atom?

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Key Concepts

Historical Atomic Models

Before Rutherford's experiment, the prevailing concept was the plum pudding model, which held that atoms were a diffuse cloud of positive charge with electrons embedded randomly within it. This model led to the expectation that an alpha particle would pass through the atom with little deflection since the positive charge was thought to be spread out uniformly.

Alpha Particle Scattering

The experiment involved directing alpha particles at a thin foil and detecting their scattering. It was expected that the paths of these particles would show only slight deflections due to the uniform distribution of charge. However, the observation of some particles bouncing back at large angles indicated unexpected strong repulsive forces at short distances, revealing discrepancies in the existing model.

Nuclear Model of the Atom

The unexpected scattering results led Rutherford to propose a new model of the atom, where a small, dense, and positively charged nucleus is surrounded by electrons. This nuclear model explained the large-angle deflections; most alpha particles passed through the atom unhindered because they missed the tiny nucleus, while those that came close experienced significant repulsion.

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