This topic summary covers Knowledge Organiser: Ionic Compounds within Ionic Compounds for GCSE Chemistry. Revise Ionic Compounds in Bonding & Structure for GCSE Chemistry with 21 exam-style questions and 21 flashcards. Use this page as part of a wider topic revision path rather than treating it as an isolated fact. It is section 12 of 12 in this topic. Use this topic summary to connect the idea to the wider topic before moving on to questions and flashcards.
Knowledge Organiser: Ionic Compounds
Key Terms
- Giant ionic lattice: regular 3D arrangement of alternating ions
- Electrostatic attraction: force between opposite charges
- Electrolyte: conducts electricity when dissolved/molten
- Brittle: shatters when force applied (layer shift → repulsion)
Must-Know Facts
- No molecules — giant lattice structure
- High MP/BP — many strong electrostatic forces
- Solid: NO conduction (ions fixed)
- Molten/dissolved: CONDUCTS (ions free to move)
- Higher charge → stronger forces → higher MP
- MgO melts at 2852°C vs NaCl at 801°C
Key Equations
- No calculation equations — focus on structure and properties
- Conduction requires free ions: solid (no) → molten/dissolved (yes)
- Higher ion charge = stronger electrostatic attraction = higher melting point
Common Mistakes
- Saying ionic compounds conduct electricity when solid: Ions are fixed in the lattice when solid — only molten or dissolved ionic compounds conduct
- Forgetting to explain WHY melting point is high: Say "many strong electrostatic forces between oppositely charged ions require a lot of energy to break"
- Saying ionic compounds are made of molecules: Ionic compounds form giant lattices — there are no discrete molecules
- Not linking ion charge to melting point: MgO has higher charge ions (Mg²⁺, O²⁻) than NaCl (Na⁺, Cl⁻) so has much stronger forces and a higher melting point
Practice questions for Ionic Compounds
What type of structure is found in all ionic compounds?
Explain why magnesium oxide conducts electricity when it is molten but not when it is solid.
Quick recall flashcards
Memory aid: When does an ionic compound conduct electricity?
Solid = stuck (ions fixed, no conduction)
Liquid = loose (ions free to move)
Solution = swimming (ions free to move)
Only liquid and solution conduct!
What is a giant ionic lattice?
A regular 3D arrangement of alternating positive and negative ions extending in all directions