In a historic experiment designed to probe atomic structure, a collimated beam of helium-4 nuclei (He2+\text{He}^{2+}He2+) was directed at a thin foil of platinum.
The vast majority of the helium-4 nuclei passed directly through the platinum target without undergoing any detectable deflection. State the fundamental conclusion regarding the structure of the platinum atom that can be deduced from this specific observation.
A minute fraction of the incoming helium-4 nuclei experienced large-angle deflections greater than 90∘90^\circ90∘. Explain how these deflections demonstrate that the platinum nucleus must carry a positive charge.