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•• The Rutherford model of the atom could explain the large-angle scattering of alpha particles because it led to very large electric fields compared to the Thomson model. To see this, note that in the Thomson model the positive charge of an atom was uniformly distributed through a sphere of the same size as the atom itself. According to this model, what would be the maximum E field (in volts/meter) produced by the positive charge in a gold atom (Z = 79, atomic radius ≈ 0.18 nm)? What is the corresponding maximum field in Rutherford’s model of the gold atom, with the positive charge confined to a sphere of radius about 8 fm? (In the Thomson model the actual field would be even less because of the electrons. Note that since ke2 = 1.44 eV · nm, it follows that ke = 1.44 V · nm.)
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