In the Rutherford gold foil experiment, what did Rutherford originally expect would happen when alpha particles were directed at the thin gold foil?

• A. Alpha particles would be deflected at large angles by the electrons in the gold atoms.
• B. Most alpha particles would bounce back directly toward the source.
• C. Alpha particles would be absorbed by the gold atoms, causing the foil to heat up.
• D. Most alpha particles would pass straight through the foil with little or no deflection.

Answer: (D)

Verified step by step guidance

1. Understand the context of the Rutherford gold foil experiment: it involved directing alpha particles at a thin sheet of gold foil to study atomic structure.
2. Recall the atomic model before Rutherford's experiment, which was the 'plum pudding model' where positive charge was thought to be spread out diffusely with electrons embedded within it.
3. Based on the plum pudding model, predict that alpha particles, being positively charged and relatively massive, would mostly pass through the foil with minimal deflection because the positive charge was not concentrated enough to cause significant scattering.
4. Recognize that Rutherford expected most alpha particles to pass straight through the foil with little or no deflection, as the electrons are very light and would not cause large-angle deflections.
5. Note that this expectation contrasts with the actual surprising result where some alpha particles were deflected at large angles, leading to the discovery of the atomic nucleus.