What makes it "giant"?
The word "giant" in chemistry means the structure extends in all directions with no set boundary. There are no NaCl "molecules" — the whole crystal IS the structure. A single grain of table salt contains about 1.2 × 10¹⁸ ions (that's over a billion billion!). The structure is continuous and regular, with each ion in a precise geometric position.
The Lattice Structure Explained:
• Each Na⁺ ion is surrounded by 6 Cl⁻ ions (above, below, left, right, front, back)
• Each Cl⁻ ion is surrounded by 6 Na⁺ ions
• This is called a "cubic" arrangement
• The pattern repeats perfectly throughout the crystal
• Opposite charges attract (Na⁺ attracts Cl⁻) — this holds it together
• Like charges repel (Na⁺ repels Na⁺) — so they stay apart
• The arrangement maximises attractions and minimises repulsions
• This is the most stable possible arrangement
Why Properties Depend on Structure:
• Many strong electrostatic attractions hold ions together
• Takes huge energy input to overcome these forces
• NaCl melts at 801°C, MgO melts at 2852°C!
• The higher the charge on ions, the stronger the attraction, the higher the melting point
• Solid: ions FIXED in position → cannot carry charge → NO conduction
• Molten: lattice broken, ions FREE to move → CAN carry charge → CONDUCTS
• Dissolved in water: same thing — ions separate and move freely → CONDUCTS
Key phrase: "ions are free to move and carry charge"
• When you hit an ionic crystal with force, layers of ions shift
• This brings like-charged ions next to each other (Na⁺ next to Na⁺)
• Like charges REPEL — the structure is pushed apart violently
• The crystal shatters rather than bending
• This is why salt crunches when you crush it!
Exam Focus: Always explain properties in terms of the STRUCTURE. Don't just say "ionic compounds have high melting points" — say "ionic compounds have high melting points BECAUSE there are many strong electrostatic forces between ions that require a lot of energy to overcome."
This deep dive covers Understanding the Giant Ionic Lattice 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 3 of 12 in this topic. Use this deep dive to connect the idea to the wider topic before moving on to questions and flashcards.
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.