IGCSE Chemistry: Chemical Bonding Practice Questions
Ionic bonding is the electrostatic attraction between oppositely charged ions formed by transferring electrons. Covalent bonding is the sharing of pairs of electrons between atoms. Metallic bonding is the attraction between positive metal ions and a sea of delocalised electrons.
Bonding sits inside Topic 2 of Cambridge IGCSE Chemistry 0620 and it underpins almost everything after it. Nearly every bonding question follows the same shape: describe the bonding, then use it to explain a physical property such as melting point or electrical conductivity. Getting full marks depends on naming the particles and the forces between them precisely.
What you need to know for Chemical Bonding
- Ionic bondingElectrons are transferred from a metal atom to a non-metal atom. The metal forms a positive ion, the non-metal forms a negative ion, and the strong electrostatic attraction between them is the ionic bond.
- Giant ionic latticeIonic compounds form a regular three dimensional lattice of alternating ions. Many strong ionic bonds must be broken to melt it, so melting points are high.
- Covalent bondingTwo non-metal atoms share one or more pairs of electrons so that each achieves a full outer shell.
- Simple molecular structuresSmall covalent molecules such as methane and water. The covalent bonds inside each molecule are strong, but the intermolecular forces between molecules are weak, so melting and boiling points are low.
- Giant covalent structuresDiamond, graphite and silicon(IV) oxide. Every atom is joined by strong covalent bonds throughout the structure, so melting points are very high.
- Metallic bondingA lattice of positive metal ions in a sea of delocalised electrons. The delocalised electrons explain electrical conductivity, and the layers sliding over one another explain malleability.
IGCSE Chemistry Chemical Bonding questions and answers
4 exam-style questions written to the 0620 syllabus. Try each one on paper first, then open the worked answer to check your method against the marks.
Describe the formation of magnesium chloride from magnesium and chlorine atoms in terms of electron transfer, and give the formula of each ion.
Show the worked answer
- Magnesium has the electronic structure 2,8,2 and needs to lose two electrons to reach a full outer shell.
- Chlorine has the structure 2,8,7 and needs to gain one electron to reach a full outer shell.
- One magnesium atom therefore transfers one electron to each of two chlorine atoms.
- The ions formed are Mg2+ and Cl-, giving the formula MgCl2, and the oppositely charged ions are held together by strong electrostatic attraction.
Sodium chloride has a melting point of 801 degrees Celsius. It does not conduct electricity when solid but does conduct when molten. Explain both observations.
Show the worked answer
- Sodium chloride is a giant ionic lattice containing many strong electrostatic attractions between Na+ and Cl- ions.
- A large amount of energy is needed to overcome all of these attractions, so the melting point is high.
- In the solid the ions are held in fixed positions in the lattice and cannot move, so there are no mobile charge carriers and no current flows.
- When molten the lattice has broken down and the ions are free to move towards the electrodes, so the molten compound conducts.
Diamond and graphite are both made only of carbon atoms. Explain why graphite conducts electricity and is soft enough to use in pencils, while diamond does neither.
Show the worked answer
- In graphite each carbon atom forms three covalent bonds, leaving one outer electron per atom delocalised between the layers.
- These delocalised electrons are free to move through the structure, so graphite conducts electricity.
- Graphite is arranged in layers held together only by weak forces, so the layers slide over one another easily and graphite is soft and slippery.
- In diamond each carbon atom forms four covalent bonds in a rigid three dimensional structure. There are no delocalised electrons, so it does not conduct, and the rigid network of strong bonds makes it extremely hard.
Explain why methane, CH4, has a boiling point of about minus 162 degrees Celsius even though the bonds within the molecule are strong.
Show the worked answer
- Methane is a simple molecular substance made of separate small molecules.
- Boiling does not break the strong covalent bonds inside each molecule. It only separates one molecule from another.
- The forces between the molecules are weak intermolecular forces, so very little energy is needed and the boiling point is very low.
Common mistakes in this topic
- Mixing up intermolecular forces with covalent bonds. Melting and boiling a simple molecular substance overcomes the forces between molecules, not the bonds within them.
- Saying ionic compounds conduct when solid. They only conduct when molten or dissolved in water.
- Forgetting the charges on ions, or writing Mg2 instead of Mg2+.
- Describing metallic bonding as attraction between atoms. It is attraction between positive ions and delocalised electrons.
- Explaining hardness or conductivity without naming the structure first. State giant ionic, simple molecular, giant covalent or metallic before explaining the property.
Exam tips
- Answer every property question in two steps: name the structure and bonding, then explain the property from it.
- Use the phrase strong electrostatic attraction between oppositely charged ions. It is the wording mark schemes look for.
- In dot and cross diagrams, show only the outer shell electrons unless the question says otherwise, and use different symbols for electrons from different atoms.
- For any conductivity question, ask yourself what is free to move: ions, delocalised electrons, or nothing.
- Learn the three giant covalent structures and one use for each. Diamond for cutting tools, graphite for electrodes and lubricant, silicon(IV) oxide in glass and sand.
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Chemical Bonding FAQs
What is the difference between ionic and covalent bonding?
Ionic bonding transfers electrons from a metal atom to a non-metal atom, producing oppositely charged ions held together by electrostatic attraction. Covalent bonding shares pairs of electrons between non-metal atoms. As a rule of thumb, metal plus non-metal gives ionic, and non-metal plus non-metal gives covalent.
Why do ionic compounds conduct electricity only when molten or dissolved?
Electrical conduction requires charged particles that are free to move. In a solid ionic lattice the ions are locked in fixed positions. Melting or dissolving breaks the lattice down and releases the ions, which can then move towards the electrodes and carry the current.
Why is graphite soft when the covalent bonds in it are strong?
The strong covalent bonds are within each layer. The layers themselves are held together only by weak intermolecular forces, so they slide over one another easily. That is why graphite works as both a pencil lead and a dry lubricant.
How should I draw a dot and cross diagram in the exam?
Show only the outer shell electrons, use dots for electrons from one atom and crosses for the other, and check that each atom ends up with a full outer shell. For ionic diagrams, draw square brackets around each ion and write the charge outside the bracket.
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Written to the published Cambridge IGCSE Chemistry (0620) syllabus. Check your school entry code and syllabus year, because Core and Extended candidates are assessed on different content. Last reviewed 2026-08-12.