In the Geiger–Marsden α-scattering experiment, the observation that MOST α-particles passed nearly UNDEFLECTED through a thin gold foil led Rutherford to conclude that
Athe atom contains a uniformly distributed positive charge
Bmost of the volume of the atom is empty space, with mass and positive charge concentrated in a small nucleus
Cα-particles experience strong inelastic collisions with atomic electrons
Datoms are tiny solid spheres of nearly uniform density
Answer & Solution
Correct answer: B. most of the volume of the atom is empty space, with mass and positive charge concentrated in a small nucleus
1. NCERT §12.2 describes the Geiger–Marsden experiment: a beam of α-particles directed at a thin gold foil.
2. Three observations: (a) most α-particles passed through with little or no deflection; (b) a small fraction were deflected through significant angles; (c) a very few (≈1 in 8000) bounced back at angles > 90°.
3. Observation (a) implies the atom is MOSTLY EMPTY — α-particles don't encounter any obstacle most of the time.
4. Observation (c) requires a heavy, charged scattering centre. Together these force the conclusion: a tiny, dense, positively-charged NUCLEUS surrounded by empty space.
5. Option A is Thomson's earlier (refuted) plum-pudding model. Option C contradicts the small-angle finding. Option D is the pre-Rutherford solid-sphere view.
_Source: NCERT Class 12 Physics Part 2, Ch 12 "Atoms", §12.2 (Alpha-Particle Scattering and Rutherford's Nuclear Model), p. 1–2._
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