Question

In Rutherford's experiment, a thin gold foil was bombarded with alpha particles. According to Thomson's 'plum-pudding' model of the atom, what should have happened?

Answer 1

Rutherford's experiment:

• Rutherford has performed an experiment, directing high-energy streams of α-particles from a radioactive source at a thin foil of heavy atoms of Gold, and to study the deflection caused to the α-particles, he placed a fluorescent Zinc sulfide screen around the thin gold foil.
• This experiment showed that matter is almost empty and that the positive charge and most of the mass of atoms are concentrated in a small region called the nucleus.

Thomson's 'plum-pudding' model of the atom:

• According to 'Thomson's Plum-Pudding model, a positive charge is spread over a sphere in which the electrons are embedded to make the atom as a whole neutral.

Rutherford's experiment observation considering Thomson's 'plum-pudding' model of the atom:

• In Rutherford's experiment, if thin gold foil was bombarded with alpha particles, the result that should have been obtained considering the Thomson's Plum-Pudding model is given as:
• The α-particles were bombarded over the neutral-charge sphere, where the α-particles should have passed through the foil with a little deflection or straight because α particles are positively charged $\left({\mathrm{He}}^{2+}\right)$ particles and hence, they would have experienced no net force on them as the charge would have been uniformly spread.
• But that wasn't the case and the alpha particles were deflected, disapproving the Thomas' model of the atom.