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2 marksModels of the Atom

CSEC Physics · 1990 · Paper 2 · Question 3(a)(ii)

Figure 5 shows the Geiger-Marsden experiment where alpha-particles in a vacuum strike a thin gold foil.

Why was a vacuum necessary?

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Other parts of this question

  1. 3(a)(i)State the composition of an alpha-particle.[2 marks]
  2. 3(a)(iii)How were the alpha-particles detected?[1 mark]
  3. 3(a)(iv)Explain why most of the alpha-particles were able to pass through the foil undeviated.[2 marks]
  4. 3(a)(v)Name ONE scientist who had proposed another model of the atom just before this one, and briefly describe that model.[2 marks]
  5. 3(b)Given the nuclear reactions: 216_84 Po -> 212_82 Pb + X and 212_82 Pb -> 212_83 Bi + Y, name the emissions X and Y and write the symbols for them.[4 marks]
  6. 3(c)The activity of a sample of a radioactive element decreases to 1/4 of its original value in one hour. Calculate the half-life of the sample.[3 marks]

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