Which of the following best describes Rutherford's contribution to the atomic model based on his gold foil experiment?

• A. He identified the existence of neutrons within the nucleus.
• B. He discovered that electrons orbit the nucleus in fixed energy levels.
• C. He suggested that atoms are indivisible and solid spheres.
• D. He proposed that atoms have a small, dense, positively charged nucleus.

Answer: (D)

Verified step by step guidance

1. Recall the historical context of atomic models before Rutherford's experiment, such as the 'plum pudding' model which suggested atoms were diffuse clouds of positive charge with embedded electrons.
2. Understand the setup of Rutherford's gold foil experiment: alpha particles were directed at a thin sheet of gold foil, and their scattering patterns were observed.
3. Analyze the key observations: most alpha particles passed through the foil with little deflection, but a small fraction were deflected at large angles, some even bouncing back.
4. Interpret these observations to conclude that atoms must have a small, dense, positively charged center (nucleus) that repels the positively charged alpha particles, while most of the atom is empty space allowing most particles to pass through.
5. Recognize that this led to the nuclear model of the atom, replacing earlier models and establishing the concept of a central nucleus containing most of the atom's mass and positive charge.