HSC Chemistry — Module 1
Ionic Bonding — Flashcards & Quiz
Ionic bonds form through the electrostatic attraction between positive and negative ions, typically between a metal and non-metal. HSC Chemistry Module 1 expects you to predict ionic formulas from group positions, explain lattice energy trends, and link the 3D lattice structure to observed properties — high melting point, brittleness, conductivity only when molten or dissolved, and solubility in polar solvents.
Key Points
- Ionic bonds form between metals (lose electrons → cations) and non-metals (gain electrons → anions) via electrostatic attraction.
- Ionic formula prediction: balance charges so the compound is neutral — e.g. Mg²⁺ + Cl⁻ → MgCl₂ (you need two chlorides per magnesium).
- Lattice energy = energy released when gaseous ions form a crystal; higher for smaller, more-charged ions (follows Coulomb's law).
- Properties: high melting point (strong lattice), brittle (shift a plane and like charges repel), conducts only when molten or dissolved (ions free to move).
- Solubility: ionic compounds generally dissolve in polar solvents like water (hydration energy overcomes lattice energy) but not in non-polar solvents.
- Naming: cation first, then anion with "-ide" suffix. Variable oxidation states use Roman numerals (e.g. Iron(III) oxide = Fe₂O₃).
Common Mistakes to Avoid
- Writing ionic formulas with the wrong charge balance — Mg²⁺ needs 2Cl⁻, not 1.
- Forgetting that ionic solids don't conduct electricity — they only conduct when molten or dissolved.
- Confusing lattice energy (release on formation) with ionisation energy (absorbed to remove electrons).
- Mixing up solubility rules for ionic compounds — most group 1 salts are soluble, most transition metal hydroxides are not.
- Drawing incorrect lattice structures — usually they're depicted as alternating cations and anions in a 3D array.
Exam Strategy
HSC Module 1 ionic bonding questions ask you to (1) predict formulas, (2) link structure to properties, or (3) compare ionic with covalent bonding. Structure: predict the charges of each ion from its group position, balance to form a neutral formula, link the 3D lattice to properties (high MP, brittleness, conductivity only when free to move).
Sample Flashcards
Q1: Describe ionic bonding and the properties of ionic compounds.
Ionic bonds form when electrons are transferred from a metal to a non-metal, creating oppositely charged ions (cations + anions) held together by electrostatic attraction in a crystal lattice. Properties: high melting/boiling points, hard and brittle, conduct electricity when molten or dissolved (mobile ions), soluble in water.
Q2: What is a lattice energy and how does it relate to ionic compound stability?
Lattice energy is the energy released when gaseous ions come together to form an ionic crystal lattice. Higher lattice energy = more stable compound = higher melting point. Lattice energy increases with higher ion charges and smaller ion sizes (stronger electrostatic attraction).
Sample Quiz Questions
Q1: Ionic compounds conduct electricity in the solid state.
Answer: FALSE
Solid ionic compounds do NOT conduct because ions are fixed in the crystal lattice. They conduct when molten or dissolved because ions become mobile.
Q2: Ionic bonds form between metals and non-metals through electron transfer.
Answer: TRUE
Metals lose electrons (form cations) and non-metals gain electrons (form anions). The electrostatic attraction between these ions is an ionic bond.
Q3: Lattice energy increases when ion charges increase and ion sizes decrease.
Answer: TRUE
Higher charges and smaller ions mean stronger electrostatic attraction (Coulomb's law), resulting in greater lattice energy and higher melting points.
Revision Tip
Formula prediction is drillable — build a Revizi flashcard deck with 15+ binary ionic compounds and their correct formulas.
Related Concepts
Last updated: March 2026 · 2 flashcards · 3 quiz questions