AQA GCSE Chemistry 8462: Chemical bonds and ionic compounds – Practice Questions

These are original questions written for Marlbridge, for revision and practice on this content. They are not reproduced past-paper questions, and they do not replicate the exam’s exact structure, question count or mark tariffs – examination boards hold copyright in their own papers. Use these alongside the official past papers from your board or school.

These questions cover 4.2.1.1 Chemical bonds and 4.2.1.3 Ionic compounds from the AQA GCSE Chemistry (8462) specification, for teaching from September 2016 onwards and exams in 2018 onwards (version 1.1). This content is assessed on Paper 1 at Foundation and Higher Tier. Neither subsection has (HT only) content, so every question here suits both tiers. Question 12 also draws on ion charges from 4.2.1.2.

These questions are different from the chemical bonds and ionic bonding practice questions, which focus on electron transfer and dot and cross diagrams. Revise first with the chemical bonds and ionic compounds study guide or the revision notes. Course hub: AQA GCSE Chemistry. Checklist: printable checklist.

Questions

1. State the particles involved in each type of strong bond.

(a) Ionic bonding [1] (b) Covalent bonding [1] (c) Metallic bonding [1]

2. Name the type of bonding in each substance: lithium fluoride, oxygen (O₂), zinc, carbon dioxide. [4]

3. Explain how a covalent bond holds the two atoms together in a fluorine molecule, F₂. [3]

4. Calcium oxide has ionic bonding. Calcium metal has metallic bonding. Give one similarity and two differences between these two types of bonding. [3]

5. A student writes: “Solid potassium chloride is made of KCl molecules. Each K⁺ ion is bonded to one Cl⁻ ion.” Explain what is wrong with this statement. [3]

6. Four structure diagrams are described.

• W: separate groups of three atoms, each joined by two lines.
• X: a regular grid of two kinds of particle, labelled 2+ and 2−, alternating, cut off at the edges.
• Y: one kind of positive particle in rows, with e⁻ symbols between them.
• Z: one kind of atom, every atom joined to four others by lines.

(a) Which diagram shows an ionic compound? [1] (b) Give two features of that diagram that show it is a giant ionic structure. [2] (c) Explain why diagram Y does not show an ionic compound, even though it contains charged particles. [2]

7. The diagram shows part of one layer of an ionic compound. Ca = calcium ion, Br = bromide ion.

Br   Br   Br   Br
   Ca        Ca
Br   Br   Br   Br
   Ca        Ca

Work out the empirical formula. Use the charges Ca²⁺ and Br⁻ to show your formula is neutral. [3]

8. A ball and stick model of part of an ionic lattice contains 6 aluminium ions (Al³⁺) and 9 oxide ions (O²⁻).

(a) Work out the empirical formula of the compound. [2] (b) Show that the charges in your formula balance. [1] (c) Give one limitation of a ball and stick model for showing an ionic lattice. [1]

9. A model of magnesium oxide is built in the same arrangement as sodium chloride, as a 3 × 3 × 3 cube of 27 ions. It contains 14 oxide ions and 13 magnesium ions. A student writes the formula Mg₁₃O₁₄.

(a) Explain why the model gives an uneven count. [2] (b) Magnesium is in Group 2 and oxygen is in Group 6. Use the ion charges to give the correct empirical formula. [2]

10. A dot and cross diagram is often used for sodium chloride.

(a) State one thing a dot and cross diagram shows well. [1] (b) Give two limitations of a dot and cross diagram as a representation of solid sodium chloride. [2]

11. Sodium chloride can be represented by a ball and stick model, a two-dimensional diagram and a three-dimensional space-filling model. Evaluate these three representations of the giant ionic structure of sodium chloride. [7]

12. Potassium (Group 1) reacts with sulfur (Group 6) to form potassium sulfide.

(a) Name the type of bonding in potassium sulfide and give a reason. [2] (b) Give the charge on a potassium ion and on a sulfide ion. [2] (c) A model of part of the lattice contains 12 potassium ions and 6 sulfide ions. Work out the empirical formula. [2] (d) Describe the structure of solid potassium sulfide and the forces holding it together. [2]

Answers

1. (a) Oppositely charged ions [1] (b) Atoms that share pairs of electrons [1] (c) Atoms that share delocalised electrons [1] Examiner insight: For (b), “atoms sharing electrons” without “pairs” may not score; in (c) the key word is “delocalised”, and naming ions alone for metallic bonding is not the answer the specification gives.

2. Lithium fluoride: ionic [1]. Oxygen: covalent [1]. Zinc: metallic [1]. Carbon dioxide: covalent [1] Examiner insight: Each substance is a separate mark, so one slip costs only one mark – but oxygen is the usual trap: a non-metallic element is covalent, not “no bonding”.

3. The two atoms share a pair of electrons (one from each atom) [1]. There is an electrostatic attraction [1] between the shared pair (negative) and the nuclei of both atoms (positive) [1]. Examiner insight: “Share electrons” earns the first mark at most; the explanation marks need the attraction and what it acts between – “both nuclei”, not “both atoms”.

4. Similarity: both are strong electrostatic attractions between opposite charges [1]. Differences: in calcium oxide electrons are transferred, forming positive and negative ions [1]; in calcium the outer electrons are delocalised and shared through the structure, with no negative ions [1]. Examiner insight: Each difference needs both sides stated or clearly implied; “ionic has ions” with nothing said about the metal scores nothing for that point.

5. Potassium chloride is a giant structure (lattice) of ions, not molecules [1]. Each K⁺ ion is attracted to all the Cl⁻ ions around it, not to one [1], because the electrostatic forces act in all directions in the lattice [1]. Examiner insight: You must correct both errors in the statement – the word “molecules” and the one-to-one bonding – to reach full marks.

6. (a) X [1] (b) Any two: two types of particle with opposite charges (ions) [1]; a regular, repeating (alternating) arrangement that continues beyond the drawing, so it is giant / has no separate molecules [1]. (c) Y has only positive particles and delocalised electrons [1]; there are no negative ions, so it shows metallic bonding [1]. Examiner insight: In (c) “it has charges” is not the issue; marks come from saying what is missing (negative ions) and naming the bonding it does show.

7. Counting: 8 bromide ions and 4 calcium ions, so Ca : Br = 4 : 8 = 1 : 2 [1]. Empirical formula CaBr₂ [1]. Charges: (+2) + 2 × (−1) = 0 [1] Examiner insight: A correct formula with no count shown can lose the method mark; write the metal first and use a subscript, not “CaBr2” written as “Ca1Br2” or “Br2Ca”.

8. (a) Al : O = 6 : 9 [1] = 2 : 3, so Al₂O₃ [1] (b) 2 × (+3) = +6 and 3 × (−2) = −6, total 0 [1] (c) Any one: the sticks suggest bonds between particular pairs of ions, but forces act in all directions; ions are shown far apart when they are closely packed; ion sizes may not be to scale; it shows only a small part of the lattice [1] Examiner insight: “It isn’t realistic” gets no credit in (c); name the feature (sticks, gaps, sizes or fragment) and say why it misleads.

9. (a) The model is a small piece of the lattice, so ions at the corners, edges and faces do not split evenly between the two types [1]. A real crystal contains so many ions that the pattern repeats and the numbers are equal [1]. (b) Mg²⁺ and O²⁻ [1], so a 1 : 1 ratio is neutral: MgO [1] Examiner insight: In (b) the charges must be stated or used to earn the first mark; an answer of MgO with no reasoning scores only the final mark.

10. (a) Which electrons are transferred / the charge on each ion [1] (b) Any two: it shows only one pair of ions, not the giant lattice [1]; it does not show the 3D arrangement or that forces act in all directions [1]; it does not show the relative sizes of the ions. Examiner insight: Two limitations must be two different ideas; “doesn’t show 3D” and “doesn’t show the shape” are likely to be treated as the same point.

11. Credit any valid points, up to the maximum: Ball and stick: shows the 3D arrangement and the alternating pattern of ions [1]; but the sticks suggest bonds between pairs, when the forces act in all directions, and ions are shown too far apart [1]. 2D diagram: shows the alternating pattern and the 1 : 1 ratio clearly [1]; but it shows only one layer, so ions above and below (and forces in those directions) are missing [1]. Space-filling: shows the relative sizes of Na⁺ and Cl⁻ and how closely packed they are [1]; but inner ions are hidden and no forces are shown, so the arrangement is hard to see [1]. Conclusion: every model shows only a tiny fragment of a lattice with an enormous number of ions, so more than one representation is needed to show the whole picture [1] Examiner insight: “Evaluate” needs strengths and limitations of each model plus a judgement; listing only limitations, or giving no conclusion, caps the mark well below 7.

12. (a) Ionic [1]: potassium is a metal and sulfur is a non-metal [1] (b) Potassium ion 1+ (K⁺) [1]; sulfide ion 2− (S²⁻) [1] (c) K : S = 12 : 6 = 2 : 1 [1], so K₂S [1] (d) A giant lattice of K⁺ and S²⁻ ions in a regular arrangement [1], held by strong electrostatic forces of attraction between oppositely charged ions acting in all directions [1] Examiner insight: Part (c) is marked from the count, so a wrong charge in (b) does not cost marks there; the ratio must still be simplified, and “K₁₂S₆” scores only the method mark.

Where marks are usually lost

• Writing “sharing electrons” for covalent bonding without “pair” or without saying what the pair is attracted to.
• Classifying a non-metallic element such as oxygen or bromine as having no bonding.
• Classifying an alloy as ionic because it contains two different elements.
• Using the word “molecule” for sodium chloride or any other ionic compound.
• Describing ionic forces as acting between one pair of ions rather than in all directions.
• Reading positive particles among electrons as ionic: an ionic diagram must have negative ions.
• Generic limitations (“not realistic”, “not accurate”) with no specific feature named.
• Leaving an empirical formula as a raw count (K₁₂S₆) or writing the non-metal first.
• On “evaluate” questions, giving only drawbacks and no judgement.

Next steps

• Chemical bonds and ionic compounds revision notes
• Chemical bonds and ionic compounds study guide
• Chemical bonds and ionic bonding revision notes
• AQA GCSE Chemistry course hub
• Printable checklist
• All free 10-minute diagnostics
• Book a free trial class

Official syllabus

AQA GCSE Chemistry (8462) specification, for teaching from September 2016 onwards, exams in 2018 onwards, version 1.1 (4 October 2019), published by AQA – sections 4.2.1.1 Chemical bonds and 4.2.1.3 Ionic compounds.