Understanding the Discovery of the Atomic Nucleus
Question:
(3 pts) Which of the following experiments showed that the atomic nucleus is very small compared to the size of the whole atom?
- Rutherford Backscattering
- Blackbody Radiation
- Compton Scattering
- Photoelectric Effect
- Electron Diffraction
Answer:
The correct answer is: a) Rutherford Backscattering
Explanation:
Rutherford’s gold foil experiment was the key experimental evidence that revealed the structure of the atom. In this experiment, alpha particles were directed at a very thin sheet of gold foil.
Rutherford’s gold foil experiment was the key experimental evidence that revealed the structure of the atom. In this experiment, alpha particles were directed at a very thin sheet of gold foil.
Observations:
Most alpha particles passed straight through the foil with no deflection, while a few were deflected at very large angles — some even rebounding backward.
Most alpha particles passed straight through the foil with no deflection, while a few were deflected at very large angles — some even rebounding backward.
Conclusion:
These observations were incompatible with the then-accepted “plum pudding model” of the atom. Instead, Rutherford concluded:
These observations were incompatible with the then-accepted “plum pudding model” of the atom. Instead, Rutherford concluded:
- Most of the atom is empty space.
- A tiny, dense region at the center — the nucleus — contains nearly all of the atom’s mass and positive charge.
None of the other experiments listed provided any direct evidence about the size or structure of the atomic nucleus:
- Blackbody Radiation: Helped develop quantum theory, but unrelated to atomic structure.
- Compton Scattering: Showed photon-particle interactions.
- Photoelectric Effect: Demonstrated particle nature of light.
- Electron Diffraction: Confirmed wave nature of electrons, not nuclear structure.
✅ Final Answer:
Rutherford Backscattering — the experiment that proved the atomic nucleus is a small, dense core within the atom.