Which of the following was a key conclusion from Rutherford's gold foil experiment?

• A. All alpha particles pass straight through the gold foil without deflection.
• B. Most of the atom's mass and positive charge are concentrated in a small nucleus.
• C. Atoms are solid spheres with no internal structure.
• D. Electrons are evenly distributed throughout the atom like plums in a pudding.

Answer: (B)

Verified step by step guidance

1. Recall the setup of Rutherford's gold foil experiment: alpha particles were directed at a thin sheet of gold foil to observe their scattering behavior.
2. Understand the expected results based on the plum pudding model, which predicted that alpha particles would mostly pass through with minimal deflection because positive charge was thought to be spread out evenly.
3. Analyze the actual observations: most alpha particles passed through the foil, but some were deflected at large angles, and a few even bounced back.
4. Interpret these results to conclude that the atom's positive charge and most of its mass must be concentrated in a very small, dense region (the nucleus), rather than being spread out.
5. Recognize that this conclusion led to the nuclear model of the atom, replacing earlier models like the plum pudding model.