Gold is a metal used in jewellery and in electronic circuit boards. Gold is malleable, has a high melting point, and conducts electricity. Explain these properties in terms of metallic bonding.

Edexcel A-Level Chemistry (9CH0) — 2.3 Metallic bonding · Explain · 5 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Gold is used in jewellery because it can be beaten into thin sheets without cracking. It is also used in electronic circuit boards because it conducts electricity reliably. Gold has a melting point of 1064 °C.

Model answer (5 marks)

Gold is a metal with a lattice of positive ions surrounded by a sea of delocalised electrons. The strong electrostatic attraction between the ions and the electrons gives the metal a high melting point – a large amount of energy is required to break these attractions. The delocalised electrons are free to move, so gold conducts electricity. Because the ions can slide past one another while the electrons keep the attraction, gold is malleable.

Examiner tips

Use the phrase ‘lattice of positive ions surrounded by a sea of delocalised electrons’.
Explain that the high melting point is due to strong electrostatic attractions and the energy needed to overcome them.
Mention that free delocalised electrons allow electrical conductivity.
State that ion layers can slide over each other while electrons maintain attraction, giving malleability.

Common mistakes

Confusing the role of delocalised electrons with that of the ions in conductivity.
Forgetting to link the high melting point to the strength of electrostatic attractions.
Describing malleability as a property of the ions alone, ignoring the stabilising role of delocalised electrons.

Mark scheme (5 marks)

Metallic bonding consists of a lattice of positive metal ions surrounded by a sea of delocalised electrons
Gold has a high melting point because there are strong electrostatic attractions between the positive ions and the delocalised electrons
A large amount of energy is needed to overcome these strong electrostatic attractions, explaining the high melting point
Gold conducts electricity because the delocalised electrons are free to move through the lattice
Gold is malleable because the layers of positive ions can slide over one another without breaking the metallic bonds, as the delocalised electrons maintain the attraction throughout

Key terms in this question

metallic bonding · malleable