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Chapter 3 Practice Paper: Atomic Structure — question paper

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QQ/S3CH/CH3

Secondary 3 · Chemistry (G2 / G3)

Chapter 3 Practice Paper

Atomic Structure

Duration: 40 minutes
Total: 30 marks
Name:
Class:
Register No.:
Date:

READ THESE INSTRUCTIONS FIRST

  • Write your name, class and register number in the spaces at the top of this page.
  • Answer all questions.
  • Give numerical answers correct to 3 significant figures unless stated otherwise, with units where a quantity is calculated.
  • Chemical equations should be balanced, with state symbols shown where the question asks for them.
  • The number of marks is given in brackets [ ] at the end of each question or part question.
  • The total number of marks for this paper is shown on its cover.

Original practice material written for the MOE Chemistry syllabus. It is not an official MOE or school examination paper. Chapter 3 (sub-atomic particles, isotopes, relative atomic mass, configurations, ions).

For Examiner’s Use
Section A/ 10
Section B/ 20
Total/ 30

Section A: Multiple-choice questions[10 marks]

Choose the one correct answer for each question.

  1. 1

    An atom of sodium is Na-23 (Z = 11). It contains

    1. A11 protons, 12 neutrons, 11 electrons
    2. B11 protons, 11 neutrons, 11 electrons
    3. C12 protons, 11 neutrons, 12 electrons
    4. D11 protons, 23 neutrons, 11 electrons
    ( )
  2. 2

    Which description of the neutron is correct?

    1. Acharge 0, mass 1
    2. Bcharge +1, mass 1
    3. Ccharge −1, mass negligible
    4. Dcharge 0, mass negligible
    ( )
  3. 3

    Isotopes of an element must have the same number of

    1. Aneutrons
    2. Bnucleons
    3. Cprotons
    4. Dnucleon numbers
    ( )
  4. 4

    A sample of iron is 5.8% Fe-54, 91.7% Fe-56 and 2.5% Fe-57 (values rounded). Its relative atomic mass is closest to

    1. A54.9
    2. B55.9
    3. C56.9
    4. D55.5
    ( )
  5. 5

    The oxide ion O²⁻ and the neon atom have the same

    1. Anumber of neutrons
    2. Bnucleon number
    3. Cnumber of electrons
    4. Dcharge
    ( )

Section B: Structured questions[20 marks]

Answer all questions in the spaces provided. Show your working for all abundance calculations and give answers to 3 significant figures where appropriate.

  1. 1

    Lithium has two isotopes: Li-6 (7.6%) and Li-7 (92.4%).

    1. (a)

      Define the term isotope.

      [1]
    2. (b)

      Show that the relative atomic mass of lithium is 6.92, using the abundances given.

      [3]
  2. 2

    Chlorine gas, Cl2, is made of covalent molecules of the two isotopes Cl-35 (A) and Cl-37 (B) in a 3 : 1 abundance ratio.

    1. (a)

      State the proton number and the number of neutrons in each of isotope A and isotope B.

      [2]
    2. (b)

      List the three possible molecular masses of Cl2 molecules in this gas, in order.

      [1]
    3. (c)

      Explain why the three kinds of molecule have identical chemical properties.

      [2]
  3. 3

    Calcium (Z = 20) reacts with chlorine (Z = 17) to form calcium chloride.

    1. (a)

      Write the electronic configurations of a calcium atom and a chlorine atom.

      [2]
    2. (b)

      State the formula of the calcium ion and the chloride ion, and the number of electrons in each.

      [2]
    3. (c)

      Hence explain why the formula of calcium chloride is CaCl2 and not CaCl.

      [2]
  4. 4

    A nuclide of element E is written with A = 31 and Z = 15.

    1. (a)

      State the number of protons, neutrons and electrons in a neutral atom of E.

      [1]
    2. (b)

      Write the electronic configuration of E.

      [1]
    3. (c)

      Predict the charge of the most common ion of E, with a reason.

      [2]
    4. (d)

      The ion from (c) has nucleon number 31. State its neutron count, with a reason.

      [1]

— End of paper —