Rutherford proposes the nuclear atom

Electrons and radioactivity showed that atoms had internal structure, but charge distribution remained debated. Geiger and Marsden, working under Rutherford, examined alpha particles passing through thin metal foil. Most deflected little, while a few scattered through large angles. Sources, foils, and scintillation observations supplied counts. Differences in particle motion offered indirect evidence about a structure too small to inspect directly through ordinary optical instruments.

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Rutherford proposed concentrated positive charge in a very small central region in 1911. Strong close encounters could then explain large deflections, while much of atomic space remained relatively empty. The model organized scattering measurements and created further questions: how could surrounding electrons move stably, and how were spectral lines produced? Explaining one experiment required additional theory for phenomena the proposed structure did not itself resolve.

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Bohr introduced quantum conditions, and later nuclear reactions and neutron discovery expanded the account. Nuclear energy and composition became fields used in medicine, materials, and energy technology. Improved probes and detectors continued inferring unseen structures through scattering. Rare large deflections in the early observations were retained rather than ignored. Their interpretation changed the model, illustrating how counting unusual outcomes could become central to a revised physical explanation.

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