Why are ionic compounds brittle?

Displacing a layer brings like charges next to each other, and the repulsion splits the crystal.

Why do ionic compounds dissolve in water?

Polar water molecules surround and stabilise the separated ions, releasing enough energy to break down the lattice.

ChemistryGCSE, IGCSE & A Level

An ionic bond is the strong electrostatic attraction between oppositely charged ions formed when electrons transfer from a metal to a non-metal.

Ionic compounds form giant lattices, so melting them requires breaking many strong attractions and the melting points are high.

They conduct electricity only when molten or dissolved, because only then are the ions free to move and carry charge.

\mathrm{Na} \rightarrow \mathrm{Na^{+}} + e^{-}, \quad \mathrm{Cl} + e^{-} \rightarrow \mathrm{Cl^{-}}

Sodium chloride forms a cubic lattice where each Na⁺ is surrounded by six Cl⁻ ions.

Include the word 'electrostatic' in every definition of ionic bonding — it is a required marking point on most boards.

Why are ionic compounds brittle?: Displacing a layer brings like charges next to each other, and the repulsion splits the crystal.
Why do ionic compounds dissolve in water?: Polar water molecules surround and stabilise the separated ions, releasing enough energy to break down the lattice.

A covalent bond is a shared pair of electrons between two non-metal atoms, held together by attraction to both nuclei.

Electronegativity is the ability of an atom to attract the shared pair of electrons in a covalent bond towards itself.

Take ionic bond from a definition to full marks with exam-board question banks, revision notes and instant step-by-step feedback from Study Coach.

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