GCSE Chemistry Bonding Notes
Bonding explains why substances have the properties they do. The three types — ionic, covalent and metallic — each come from how electrons are shared or transferred.
Key concepts
- Ionic bonding
- Transfer of electrons from a metal to a non-metal, forming oppositely charged ions held by strong electrostatic forces.
- Covalent bonding
- Sharing of electron pairs between non-metal atoms, forming molecules or giant covalent structures.
- Metallic bonding
- A lattice of positive metal ions in a sea of delocalised electrons, explaining conductivity and malleability.
- Ionic compounds have high melting points and conduct when molten or dissolved.
- Simple molecular substances have low melting points and do not conduct electricity.
- Metals conduct electricity and heat because of delocalised electrons.
Worked example
Explain why sodium chloride has a high melting point.
- 1Sodium chloride is an ionic compound with a giant ionic lattice.
- 2There are strong electrostatic forces of attraction between oppositely charged ions.
- 3A large amount of energy is needed to overcome these forces.
- 4Therefore the melting point is high.
Answer: Strong electrostatic forces in the giant ionic lattice need lots of energy to break, so the melting point is high.
Common mistakes
✗ Saying ionic compounds conduct when solid.
✓ They only conduct when molten or dissolved, because the ions must be free to move.
✗ Confusing intermolecular forces with covalent bonds.
✓ Melting a simple molecular substance breaks weak intermolecular forces, not the strong covalent bonds inside the molecule.
✗ Forgetting the word 'electrostatic' when describing ionic bonds.
✓ Examiners want 'strong electrostatic forces of attraction between oppositely charged ions'.
Quick check
Try these, then reveal the answers.
What type of bonding is between a metal and a non-metal?Reveal answer
Ionic bonding.
Why can metals conduct electricity?Reveal answer
They have delocalised electrons that are free to move.
What is shared in a covalent bond?Reveal answer
A pair of electrons.
Exam tips
- Link structure to properties — examiners reward 'because of … the substance can/cannot …'.
- Use the exact phrase 'electrostatic forces of attraction between oppositely charged ions' for ionic bonding.
- Draw dot-and-cross diagrams clearly, showing only outer electrons.
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Frequently asked questions
What are the three types of chemical bonding?+
Ionic (metal + non-metal), covalent (non-metal + non-metal) and metallic (within metals).
Why do ionic compounds only conduct when molten or dissolved?+
The ions are locked in place in the solid lattice; melting or dissolving frees them to move and carry charge.
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