Rutherford devised an experiment to fire alpha particles at thin gold foil - Edexcel - GCSE Physics - Question 8 - 2022 - Paper 1

From the graph in Figure 11, the number of particles scattered through 5° can be estimated at around 10² and those scattered through 100° at approximately 10⁰.

Thus, to find the ratio:

$\text{Ratio} = \frac{\text{Particles at } 5°}{\text{Particles at } 100°} = \frac{10^2}{10^0} = 100$

The ratio of the number of particles scattered through 5° to those scattered through 100° is approximately 100:1.

The difference in the number of particles scattered at various angles provides critical evidence for the structure of the atom:

1. Alpha Particles and Scattering: In the experiment, a small number of alpha particles were scattered at large angles, which indicated the presence of a concentrated positive mass in the atom. Most particles passed through, suggesting a lot of empty space in atoms.

2. Nucleus Presence: The presence of particles scattered at angles greater than 90° indicates that there are dense centers (nuclei) within the atoms that exert strong forces, causing elastic scattering of the alpha particles.

3. Atomic Structure: The results are consistent with the nuclear model of the atom, where most of the atom's volume is empty and the mass is concentrated in a small nucleus.

4. Comparison to Plum Pudding Model: This evidence contradicted earlier models like the plum pudding model, which proposed that positive charge was distributed evenly throughout the atom, failing to explain the significant deflections observed.

To model the scattering of alpha particles using the apparatus shown in Figure 12, students can follow these steps:

1. Setup: Place the large sheet of paper on a flat surface, ensuring it has lines 1 cm apart as a grid for prediction and recording.

2. Use of marble as a model: The marble represents an alpha particle. Students should roll the marble down the movable slope towards the paper sheet, similar to alpha particles being fired towards a gold foil.

3. Recording Scattering: As the marble interacts with the surface, it will bounce off and scatter in different directions. Students can track the angles at which the marble travels, analogous to how alpha particles scatter when they hit the gold nuclei.

4. Analyzing Results: By measuring and recording the angles of deflection, students can compare their findings to Rutherford’s experiment, discussing the patterns and implications regarding atomic structure.

One limitation of this model is that it does not accurately represent the quantum nature of particles. Alpha particles behave according to quantum mechanics, involving wave-particle duality and probabilities, which cannot be precisely modeled using classical objects like marbles.