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AS & A Level · AS/A Level

Chemistry

Atomic structure and periodicity

Name: ____________________Date: October 10, 2026
  1. 1.

    An atom has atomic number 17 and mass number 37. State its proton, neutron and electron counts when it forms a singly negative ion.

    [3 marks] · no calculator
  2. 2.

    Write the full electron configuration of a ground-state sodium atom and explain which electron is removed first.

    [3 marks] · no calculator
  3. 3.

    An element has isotopes of mass 24 (75%) and 26 (25%). Calculate its relative atomic mass and explain why the value is not a mass number.

    [3 marks]
  4. 4.

    Explain why the first ionisation energy of aluminium is lower than that of magnesium despite aluminium having more protons.

    [3 marks] · no calculator
  5. 5.

    Successive ionisation energies are 590, 1150, 4940 and 6480 kJ mol^-1. Infer the main-group valence-electron count and explain why the jump is evidence, not an exact elemental identification.

    [4 marks] · no calculator
  6. 6.

    Predict which has the smallest radius among O^2-, F^- and Na^+, and explain the ordering using electron structure rather than charge alone.

    [4 marks] · no calculator

Original, unofficial practice questions from SubjectScout — not official past-paper questions.

Marking points are indicative, not an official mark scheme. Accept equivalent valid methods and supported interpretations that address the task; award each mark once without requiring the model wording.