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NEET levelSingle correct optionDifficulty 1 of 3as001

In the gold foil experiment, a very small fraction of the alpha particles bounced back through large angles. Which conclusion was drawn mainly from this observation?

  1. AElectrons are embedded uniformly in a sphere of positive charge
  2. BPositive charge and most of the mass of the atom are concentrated in a very small central region
  3. CElectrons move only in orbits of fixed energy
  4. DAlpha particles are heavier than the atoms of gold

Answer: B

Large-angle reflection of a few heavy, positive alpha particles needs a strong repulsion from a tiny, massive, positively charged centre. A uniform positive sphere (Thomson model) cannot produce such deflections. Hence the nucleus concept.
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