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AS · Practice questions · Ionic bonding

Charges in a crystal.

Six original Cambridge-style questions on ionic bonding: electron transfer, ion configurations, lattice structure, the effect of charge and size, and the properties of ionic compounds.

Original questions All questions on this page are original work, written in the Cambridge AS & A Level style. They are not from past papers. They test the same concepts and skills the syllabus rewards.
Keep these straight

Bigger charges, smaller ions, stronger bonding.

01
Recall
[1 marks]

Define ionic bonding.

  • The electrostatic attraction between oppositely charged ions. ✓
02
Explain
[3 marks]

Describe, in terms of electrons, how magnesium and oxygen form magnesium oxide. Give the full electron configurations of both ions.

  • Each magnesium atom transfers its two 3s electrons to an oxygen atom. ✓
  • Mg2+: 1s2 2s2 2p6. ✓
  • O2−: 1s2 2s2 2p6. Both ions have the configuration of neon. ✓
03
Recall
[2 marks]

Write the formulae of the ionic compounds formed between (a) aluminium and oxygen and (b) potassium and sulfur.

  • (a) Al3+ and O2−: Al2O3, total charge 2 × (+3) + 3 × (−2) = 0. ✓
  • (b) K+ and S2−: K2S. ✓
04
Explain
[3 marks]

Magnesium oxide melts at 2852 °C but sodium chloride melts at 801 °C. Explain the difference.

  • Both are giant ionic lattices, so melting means overcoming the electrostatic attraction between ions. ✓
  • Mg2+ and O2− carry double the charges of Na+ and Cl−, and they are smaller, so the ions are closer. ✓
  • The attraction in MgO is therefore much stronger and needs more energy to overcome. ✓
05
Explain
[3 marks]

Explain why sodium chloride does not conduct electricity as a solid but does when molten or dissolved in water.

  • Conduction needs mobile charged particles. ✓
  • In the solid, the ions are held in fixed positions in the lattice and cannot move. ✓
  • When molten or in solution the lattice breaks up and the ions are free to move and carry charge. ✓
06
Explain
[2 marks]

Explain why an ionic crystal shatters when struck with a hammer.

  • The blow displaces one layer of ions relative to the next. ✓
  • Ions of the same charge are brought next to each other; they repel and the crystal splits along that plane. ✓

Mark this once you have attempted all six and checked your working. It records a Practiced badge on the topic and adds a one-time bonus. Revealing the solutions alone does not count.