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Practice · Chemistry · 2025 syllabus · S1.3

IB Chemistry S1.3 Electron configurations: practice questions

10 exam-style questions on S1.3 Electron configurations, SL and HL, 3 marked HL: 6 multiple choice, 1 data-based and 3 structured. Each one comes with the mark scheme, a model answer and the reasoning behind every mark. Free with your email.

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S1.3-01 · Paper 1A style · multiple choice · 1 mark

Outer electrons in ions

W, X, Y and Z stand for four species; the letters are not element symbols.
73W+, 3216X2−, 115Y, 2713Z3+
Which two have the same number of electrons in their outer main energy level? [1]

  1. Y and Z
  2. W and Z
  3. X and Z
  4. W and X
Show the answer and the reasoning

Answer: C. C is correct. X has 16 + 2 = 18 electrons (2,8,8) and Z has 13 − 3 = 10 electrons (2,8): both have 8 electrons in the outer level. W has 2 electrons (2) and Y, a neutral atom, has 5 (2,3). A is the trap: Y and Z are in the same group, but Z has lost its three outer electrons. B: both are positive ions, but W has 2 outer electrons and Z has 8. D: W has 2 and X has 8.

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The 10 questions in S1.3

  1. S1.3-01 Outer electrons in ionsPaper 1A style · multiple choice · 1 mark
  2. S1.3-02 Capacity of an energy levelPaper 1A style · multiple choice · 1 mark
  3. S1.3-03 Applying Pauli and HundPaper 1A style · multiple choice · 1 mark
  4. S1.3-04 Configuration of a d-block ionPaper 1A style · multiple choice · 1 mark
  5. S1.3-05 Group from successive IEsPaper 1A style · multiple choice · 1 mark · HL
  6. S1.3-06 Convergence of spectral linesPaper 1A style · multiple choice · 1 mark
  7. S1.3-07 Ionization energy against atomic radiusPaper 1B style · data-based · 5 marks
  8. S1.3-08 Ionization energy from a spectrumPaper 2 style · structured question · 5 marks · HL
  9. S1.3-09 Configurations and an exceptionPaper 2 style · structured question · 5 marks
  10. S1.3-10 Dips in first ionization energyPaper 2 style · structured question · 4 marks · HL

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Every Biology and Chemistry question here is original, written for practice in the style of the papers set since the 2025 syllabus, with invented data. Developed independently from the International Baccalaureate Organization, which has not endorsed it. Found a mistake? Email vytis@limeadmissions.com with the question id.