9701 · 3.3
Metallic bonding flashcards
Revision flashcards for Cambridge 9701 Metallic bonding (syllabus 3.3). Flip, recall, then mark a real past-paper question.
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What is metallic bonding?
The strong electrostatic attraction between a lattice of positive metal ions (cations) and a 'sea' of delocalised electrons.
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What are 'delocalised electrons'?
Outer shell electrons that are not associated with any single atom or ion, and are free to move throughout the entire metallic structure.
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Why do metals form positive ions in the metallic lattice?
Metal atoms have low ionisation energies, so they readily lose their outer shell electrons to become stable positive ions (cations).
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Explain why metals are good electrical conductors.
The mobile delocalised electrons are free to move and carry charge through the lattice when a potential difference (voltage) is applied.
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Why are metals malleable and ductile?
The layers of positive ions can slide over one another without breaking the metallic bond, as the delocalised electrons continue to hold the ions together in their new positions.
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What is the difference between malleable and ductile?
Malleable means it can be hammered or beaten into shape. Ductile means it can be drawn into a wire.
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Why do metals typically have high melting and boiling points?
A large amount of energy is required to overcome the strong electrostatic forces of attraction between the positive ions and the sea of delocalised electrons.
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How does ionic charge affect the strength of a metallic bond?
A greater positive charge on the metal ion (e.g., Mg²⁺ vs Na⁺) leads to a stronger electrostatic attraction with the delocalised electrons, resulting in a stronger bond and higher melting point.
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How does ionic radius affect the strength of a metallic bond?
A smaller ionic radius leads to a higher charge density, meaning the positive charge is more concentrated. This results in a stronger attraction to the delocalised electrons, a stronger bond, and a higher melting point.
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What is an alloy?
A mixture of a metal with one or more other elements, which are usually also metals. For example, brass is an alloy of copper and zinc.
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Why are alloys often harder and stronger than pure metals?
The different sized atoms of the alloying elements distort the regular lattice structure, making it more difficult for the layers of ions to slide over one another.