The correct option is (c).
Explanation
The discovery of the atomic nucleus established the nuclear model of the atom, fundamentally altering the understanding of atomic structure. This discovery refuted the earlier "Plum Pudding" model, which suggested a uniform distribution of positive charge and mass.Statement-wise Analysis:
- Statement 1 is Incorrect. The nucleus was discovered by Ernest Rutherford in 1911. J.J. Thomson is credited with the discovery of the electron and the proposal of the "Plum Pudding" model.
- Statement 2 is Correct. The discovery resulted from the alpha-particle scattering experiment. The observation that a tiny fraction of alpha particles were deflected at very large angles (even rebounding back) led Rutherford to conclude that the positive charge and most of the mass were concentrated in a small volume.
- Statement 3 is Correct. The experiment involved bombarding a very thin sheet of gold foil (approximately 100 nm thick) with high-energy alpha particles. Gold was selected because of its high malleability, which allowed the creation of an extremely thin target.
Key Takeaway: Ernest Rutherford discovered the nucleus through the gold foil experiment, proving that an atom consists mostly of empty space with a dense, positively charged center containing nearly all its mass.