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4 marksParticles in the Atom

CSEC Physics · 1995 · Paper 2 · Question 2(a)(ii)

Table 1 represents the first three periods of the Periodic Table of elements.

The most common isotope of boron (B) may be represented as ¹¹₅B. A boron atom has two shells of electrons, with two electrons in the first shell. In the space provided, draw a clear diagram to represent the number and distribution of protons, neutrons and electrons in a neutral ¹¹₅B atom.

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Other parts of this question

  1. 2(a)(i)The atomic number of chlorine (Cl) is 17. How many protons are there in one atom of silicon (Si)?[1 mark]
  2. 2(a)(iii)Write the symbol for another possible isotope of boron.[1 mark]
  3. 2(b)(i)By reading off values of the count rate at suitable times, show that the half-life of Sample A is constant, and find its value.[4 marks]
  4. 2(b)(ii)By considering the relevant graph, comment on the half-life of Sample B.[1 mark]
  5. 2(b)(iii)Why are the points on the graph of Sample B not exactly on the line even though the ratemeter was not faulty?[1 mark]
  6. 2(b)(iv)What difference, if any, would be noticed in the graph if Sample B were heated?[1 mark]
  7. 2(b)(v)Sample B is an isotope of thorium (Th), with a proton number of 90 and a neutron number of 142. It decays by the emission of an alpha particle to form radium…[3 marks]

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