In the Rutherford gold foil experiment, how did scientists conclude that most of an atom is empty space?

• A. Alpha particles were completely reflected back from the gold foil.
• B. Alpha particles caused the gold foil to emit visible light.
• C. All alpha particles were absorbed by the gold foil.
• D. Most alpha particles passed straight through the gold foil without deflection.

Answer: (D)

Verified step by step guidance

1. Recall the setup of the Rutherford gold foil experiment, where alpha particles (positively charged helium nuclei) were directed at a very thin sheet of gold foil.
2. Understand that if atoms were solid throughout, alpha particles would mostly be deflected or stopped by the foil, causing significant scattering or absorption.
3. Observe that in the experiment, most alpha particles passed straight through the gold foil with little or no deflection, indicating that they did not encounter any dense material in their path.
4. Note that only a small fraction of alpha particles were deflected at large angles or reflected back, suggesting the presence of a small, dense, positively charged nucleus within the atom.
5. Conclude that since most alpha particles passed through undeflected, the atom must be mostly empty space, with a tiny dense nucleus at its center.