9701 · 3.2
Ionic bonding flashcards
Revision flashcards for Cambridge 9701 Ionic bonding (syllabus 3.2). Flip, recall, then mark a real past-paper question.
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What is an ionic bond?
The strong electrostatic force of attraction between oppositely charged ions in a giant ionic lattice.
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How are ions formed in ionic bonding?
Through the transfer of one or more electrons from a metal atom (forming a cation) to a non-metal atom (forming an anion).
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What is a giant ionic lattice?
A regular, repeating three-dimensional arrangement of alternating positive and negative ions.
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Why do ionic compounds have high melting and boiling points?
A large amount of thermal energy is required to overcome the strong electrostatic forces of attraction between the ions in the giant lattice.
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Why are ionic compounds brittle?
When a force is applied, layers of ions slide over each other. This brings ions with the same charge alongside each other, causing strong repulsion that shatters the crystal.
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When do ionic compounds conduct electricity?
Only when molten (liquid) or dissolved in a solvent (aqueous). In these states, the ions are mobile and can move to carry charge.
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Why don't ionic compounds conduct electricity in the solid state?
In the solid lattice, the ions are held in fixed positions and are not free to move to act as charge carriers.
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What two factors make an ionic bond stronger?
1. Higher ionic charges (e.g., Mg²⁺O²⁻ is stronger than Na⁺Cl⁻). 2. Smaller ionic radii (e.g., Li⁺F⁻ is stronger than K⁺Br⁻). Both increase the charge density.
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What is the coordination number in an ionic lattice?
The number of nearest neighbouring ions of opposite charge that surround a given ion. In NaCl, the coordination number for both Na⁺ and Cl⁻ is 6.
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What does the chemical formula of an ionic compound, like NaCl, represent?
It is an empirical formula, representing the simplest whole-number ratio of ions in the giant lattice, not a discrete molecule.
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A common exam mistake is drawing sodium chloride as a single Na-Cl molecule. Why is this wrong?
Sodium chloride does not exist as discrete molecules. It forms a giant ionic lattice where each Na⁺ ion is surrounded by 6 Cl⁻ ions, and each Cl⁻ is surrounded by 6 Na⁺ ions.
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Write the electronic configurations for the ions formed between magnesium and oxygen.
Mg (1s²2s²2p⁶3s²) → Mg²⁺ (1s²2s²2p⁶) + 2e^{-}. O (1s²2s²2p⁴) + 2e^{-} → O²⁻ (1s²2s²2p⁶). Both ions are isoelectronic with Neon.