Chemistry • Year 11 • Module 1 • Lesson 7
Ionic Bonding and Properties
Lock in the key vocabulary, the NaCl lattice model, and the four physical-property explanations before tackling harder questions.
1. Term–definition match
The definitions below are shuffled. In the right-hand column write the matching term from this list: ionic bond, ionic lattice, lattice energy, electrolyte, cation, anion, coordination number, hydration, Coulomb’s Law, brittleness. 10 marks (1 each)
| # | Definition | Matching term |
|---|---|---|
| 1.1 | The electrostatic attraction between oppositely charged ions formed by electron transfer from a metal to a non-metal. | |
| 1.2 | A regular, repeating three-dimensional arrangement of cations and anions; no discrete molecules are present. | |
| 1.3 | The energy released when gaseous ions come together to form an ionic lattice; higher values mean stronger, higher-melting structures. | |
| 1.4 | A substance that conducts electricity when dissolved in water or melted, due to the presence of mobile ions. | |
| 1.5 | A positively charged ion formed when a metal atom loses one or more electrons. | |
| 1.6 | A negatively charged ion formed when a non-metal atom gains one or more electrons. | |
| 1.7 | The number of ions of opposite charge that surround a given ion in the lattice; in NaCl this value is 6. | |
| 1.8 | The process by which water molecules surround and stabilise individual ions when an ionic compound dissolves, pulling them off the lattice. | |
| 1.9 | The physical law stating that electrostatic force is proportional to the product of the charges and inversely proportional to the square of the distance between them. | |
| 1.10 | The tendency of an ionic solid to shatter under impact because a shift in ion layers aligns like charges, producing strong repulsion that cleaves the crystal. |
2. True or false — with correction
Circle T or F for each statement. If the statement is false, write the corrected version on the line below it. 12 marks (1 T/F + 1 correction each)
2.1 In a solid ionic compound like NaCl, the ions can move freely and so the compound conducts electricity. T / F
2.2 Ionic compounds are brittle because their lattice has no resistance to deformation. T / F
2.3 MgO has a much higher melting point than NaCl primarily because Mg²¹ and O²¯ carry charges of ±2, producing stronger electrostatic attraction than the ±1 ions in NaCl. T / F
2.4 An ionic compound does not conduct electricity as a solid because it contains no ions. T / F
2.5 In the NaCl lattice each Na¹¹ ion is surrounded by 6 Cl¯ ions in an octahedral arrangement, giving a coordination number of 6. T / F
2.6 All ionic compounds are soluble in water because the hydration energy always exceeds the lattice energy. T / F
3. Fill-in-the-blank paragraph
Use the word bank to complete the passage. Each word is used once. 9 marks (1 per blank)
Word bank:
brittle · charge · electrostatic · hydration · immobile · lattice · melting · mobile · size
In an ionic compound, oppositely charged ions are held together by strong ___________ forces in a three-dimensional ___________ structure. Because of these forces, ionic compounds have high ___________ points; greater ion ___________ and smaller ion ___________ both increase the strength of attraction and therefore raise the melting point. In the solid state, ions are ___________ in fixed positions and the compound cannot conduct electricity. When the compound melts or dissolves in water, the ions become ___________ and can carry charge. When ionic compounds dissolve, polar water molecules surround each ion in a process called ___________. Despite being hard, ionic compounds are ___________ because a shift in lattice layers aligns like charges, causing repulsion and cleavage.
4. Function recall
Answer each question in 1–2 sentences using precise terms from the lesson. 8 marks (2 each)
4.1 What structural feature of a solid ionic compound prevents it from conducting electricity?
4.2 What happens to the ionic lattice when an ionic compound is dissolved in water, and why does this allow the solution to conduct electricity?
4.3 Why does increasing the charge on the ions in an ionic compound increase the melting point?
4.4 What is the NaCl formula unit, and what does it tell us about the number of discrete molecules in a sodium chloride crystal?
5. Build a concept map
Draw labelled arrows between the six terms below to show how they connect. Each arrow must carry a linking phrase (e.g. “produces”, “increases”, “enables”). Aim for at least 6 labelled arrows. 6 marks (1 per valid labelled arrow)
Supplied terms: ionic lattice · lattice energy · ion charge · melting point · mobile ions · electrical conductivity.
Q1 — Term–definition match
1.1 ionic bond • 1.2 ionic lattice • 1.3 lattice energy • 1.4 electrolyte • 1.5 cation • 1.6 anion • 1.7 coordination number • 1.8 hydration • 1.9 Coulomb’s Law • 1.10 brittleness.
Q2 — True / false with correction
2.1 False. In solid NaCl the ions are fixed (immobile) in the lattice. They cannot move to carry charge, so solid ionic compounds do not conduct electricity. Conductivity only occurs when ions are mobile — i.e. when the compound is molten or dissolved.
2.2 False. Ionic compounds are brittle because shifting a layer of ions aligns like charges, producing strong repulsion that cleaves the crystal. They are actually very hard (resist scratching), not lacking resistance to deformation.
2.3 True.
2.4 False. Ionic solids contain many ions — the reason they do not conduct is that those ions are fixed (immobile) in the lattice, not that ions are absent. Mobile charge carriers are required for conductivity.
2.5 True.
2.6 False. Many ionic compounds are insoluble in water (e.g. BaSO4, AgCl, CaCO3). Whether an ionic compound dissolves depends on the balance between lattice energy and hydration energy; if lattice energy exceeds hydration energy, the compound is insoluble.
Q3 — Cloze paragraph
In order: electrostatic / lattice / melting / charge / size / immobile / mobile / hydration / brittle.
Q4.1 — Why solid ionic compounds don’t conduct
In a solid ionic compound, all ions are locked in fixed positions in the rigid ionic lattice. They cannot move, so there are no mobile charge carriers. Electrical conductivity requires particles that can move and carry charge — since the ions cannot do this in the solid state, the compound does not conduct.
Q4.2 — Dissolution and conductivity
When an ionic compound dissolves, polar water molecules surround each ion (hydration), pulling the ions off the lattice surface and releasing them as independent, mobile ions in solution. These mobile ions can carry charge when a voltage is applied, so the solution conducts electricity.
Q4.3 — Charge and melting point
According to Coulomb’s Law, the electrostatic force between two ions is proportional to the product of their charges. Higher ion charges produce stronger attraction, increasing the lattice energy. More thermal energy is required to overcome this attraction and allow ions to move freely — so the melting point is higher.
Q4.4 — NaCl formula and discrete molecules
The formula NaCl represents the simplest whole-number ratio of ions (1 Na+ to 1 Cl−). There are no discrete NaCl molecules in a sodium chloride crystal. Each ion is attracted to all its nearest neighbours, forming a continuous giant 3D lattice — the entire crystal is one extended structure.
Q5 — Sample concept map
Correct maps should include arrows such as:
- ion charge — determines strength of → lattice energy
- lattice energy — determines → melting point
- ionic lattice — breaks down to release → mobile ions
- mobile ions — enable → electrical conductivity
- ionic lattice — has → lattice energy
- electrical conductivity — requires → mobile ions
Award 1 mark per valid labelled arrow (minimum 6, maximum 6 marked).