Answer:
Ernest Rutherford used alpha particles in his famous gold foil experiment to test the Plum Pudding Model of atomic structure because they have a high energy and a large mass.
The Plum Pudding Model proposed by J.J. Thomson suggested that atoms consisted of a uniform, positively charged sphere with negatively charged electrons embedded within it, much like plums in a pudding. However, Rutherford's observations of the scattering of alpha particles as they passed through the gold foil showed that the Plum Pudding Model was incorrect.
When Rutherford directed a beam of alpha particles at a thin sheet of gold foil, he expected the alpha particles to pass straight through or be slightly deflected by the electrons in the gold atoms. However, he observed that a small fraction of the alpha particles were deflected at large angles or even bounced back in the direction from which they came. This could only be explained if the mass of the atom was concentrated in a small, positively charged nucleus at the center, surrounded by mostly empty space.
The reason that Rutherford used alpha particles in his experiment was because their high energy and large mass allowed them to penetrate the atoms of the gold foil and interact with the positively charged nucleus, revealing its presence and disproving the Plum Pudding Model.
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