What did Ernest Rutherford’s gold foil experiment demonstrate about the structure of an atom?

• A. Protons and neutrons are arranged in fixed orbits around the nucleus.
• B. Electrons are evenly distributed throughout a positively charged sphere.
• C. Most of the atom's mass and all of its positive charge are concentrated in a small nucleus.
• D. Atoms are indivisible and cannot be broken down into smaller particles.

Answer: (C)

Verified step by step guidance

1. Understand the context of Rutherford's gold foil experiment, which involved firing alpha particles at a thin sheet of gold foil to observe their scattering patterns.
2. Recall the expectations before the experiment: according to the plum pudding model, alpha particles were expected to pass through with minimal deflection because positive charge was thought to be spread out evenly.
3. Analyze the key observation: while most alpha particles passed straight through, some were deflected at large angles, and a few even bounced back, indicating a concentrated positive charge.
4. Interpret the results: the large deflections suggested that the positive charge and most of the atom's mass are concentrated in a very small, dense region called the nucleus.
5. Conclude that Rutherford's experiment disproved the plum pudding model and demonstrated that atoms have a small, dense nucleus containing protons (and later discovered neutrons), with electrons orbiting around it.