How ideas about the atom developed from Thomson’s “plum pudding” to Rutherford’s nuclear atom, the Geiger–Marsden alpha-scattering experiment, Bohr’s shell model and Chadwick’s neutron.
5 narrated scenes. Press play, listen and read along — the points appear as they are explained. Use ‹ Prev / Next › or the scene bar to jump to any scene.
Rutherford said that firing alpha particles at gold foil and seeing some bounce back was like firing a large shell at tissue paper and having it come back. That surprise changed the picture of the atom.
Narration uses your device’s built-in voice. No sound? Switch to “Captions only” — the captions advance on their own.
Fire alpha particles at a thin gold foil and see how they scatter.
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Discovered the electron; plum-pudding model.
Alpha particles fired at thin gold foil.
Most pass through; a few deflected; very few rebound.
Mostly empty space; small, dense, positive nucleus holding almost all the mass.
Nuclear model of the atom.
Electrons in fixed energy levels (shells).
Discovered the neutron.
Protons and neutrons (nucleons) of about equal mass.
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8 items modelled on real CSEC Paper 1 questions. Choose one answer for each, then check. Aim for 80% or better. Work each item on paper first.
Write full answers, then reveal the mark scheme and tick the points you earned (14 marks in total). Show all your working — method marks count. Your answers are saved on this device.
Question 1 [14 marks]
In the Geiger–Marsden experiment alpha particles were directed at a thin gold foil in a vacuum.
(a) (a) Name the scientist who proposed the plum-pudding model and describe the model. [3]
(b) (b) State three observations made in the experiment. [3]
(c) (c) State a conclusion for each observation in (b). [3]
(d) (d) Explain why the experiment was carried out in a vacuum. [1]
(e) (e) State the contribution of (i) Bohr and (ii) Chadwick. [2]
(f) (f) Explain why the plum-pudding model was abandoned. [2]
Find these in your own past-paper booklets for extra timed practice. Items above are written in the style of these papers; any adapted from a specific question say so.