 The figure depicts Rutherford's $\alpha$-particle scattering experiment. The most striking observation was:
AAll $\alpha$-particles were absorbed by the foil
BMost $\alpha$-particles passed nearly straight, but a few were deflected at very large angles
CAll $\alpha$-particles passed through the foil undeflected
DThe $\alpha$-particles emerged from the foil as visible light
Answer & Solution
Correct answer: B. Most $\alpha$-particles passed nearly straight, but a few were deflected at very large angles
Rutherford's key finding (1911): most $\alpha$-particles passed nearly straight through the thin gold foil (so the atom is *mostly empty space*), but a tiny fraction were deflected at very large angles — some even bouncing back. Rutherford famously remarked it was "as if you fired a 15-inch shell at tissue paper and it came back and hit you."
This forced the conclusion that the positive charge and most of the mass of the atom are concentrated in a tiny, dense **nucleus** — and overturned Thomson's plum-pudding model.
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