### Correct Option: B. The gold nucleus is positively charged and is concentrated in a tiny volume. #### Detailed Explanation: The Rutherford scattering experiment, conducted by Ernest Rutherford in 1909, was pivotal in shaping our understanding of atomic structure. Here’s a step-by-step breakdown of why option B is the correct answer: 1. **Setup of the Experiment**: In the experiment, a beam of alpha particles (which are positively charged helium nuclei) was directed at a very thin foil of gold. The expectation was that, due to the prevailing plum pudding model of the atom (which suggested that electrons were distributed throughout a positively charged "soup"), the alpha particles would pass through with minimal deflection. 2. **Observations**: Surprisingly, while most alpha particles passed through the gold foil with little to no deflection, a small fraction were deflected at large angles, and some even bounced back toward the source. This was unexpected and indicated that something significant was happening at a very small scale. 3. **Conclusion Drawn**: Rutherford concluded that the atom must have a small, dense, positively charged center, which he termed the nucleus. The fact that some alpha particles were deflected at large angles suggested that they were encountering something much more massive and concentrated than the surrounding "soup" of electrons. 4. **Why Option B is Correct**: - **Positively Charged**: The deflection of the positively charged alpha particles indicated that they were repelled by a positively charged center, which must be the nucleus of the gold atoms. - **Concentrated in a Tiny Volume**: The large deflections could only occur if the nucleus was very small compared to the overall size of the atom. If the nucleus were spread out, the alpha particles would not experience such strong repulsion. #### Why the Other Options are Incorrect: - **Option A**: "A gold nucleus contains protons, neutrons, and electrons uniformly distributed in a tiny volume." - **Why It's Wrong**: This option suggests that electrons are uniformly distributed within the nucleus, which contradicts Rutherford's findings. In reality, electrons orbit the nucleus at a distance, and the nucleus itself is composed of protons and neutrons, not electrons. - **Option C**: "The gold nucleus emitted alpha particles." - **Why It's Wrong**: The nucleus does not emit alpha particles in this context. Instead, alpha particles are used as projectiles in the experiment. The nucleus is the target that causes the deflection of the incoming alpha particles. - **Option D**: "The gold nucleus is concentrated in a tiny volume and contains alpha particles." - **Why It's Wrong**: While it is true that the nucleus is concentrated in a tiny volume, it does not contain alpha particles. Alpha particles are emitted by certain types of radioactive decay from unstable nuclei, but they are not components of the gold nucleus itself. ### Summary of Key Points: - The Rutherford experiment revealed that the atom has a small, dense, positively charged nucleus. - Most of the atom's volume is empty space where electrons are located. - The significant deflection of alpha particles indicates a concentrated positive charge in the nucleus. - The experiment led to the development of the nuclear model of the atom, replacing the plum pudding model. This understanding is crucial for grasping the fundamental structure of atoms and the principles of nuclear physics.