Ionic compounds
The giant ionic lattice
- An ionic compound is not made of separate molecules.
- The ions pack into a giant lattice — a regular, repeating pattern of alternating positive and negative ions.
Practice
An ionic compound is made of:
Ions pack into a regular giant lattice, not separate molecules.
Properties explained
| Property | Reason |
|---|---|
| high melting/boiling point | strong attraction between ions needs a lot of energy to break |
| does not conduct when solid | ions are fixed in place, can't move |
| conducts when molten or dissolved | ions are now free to move and carry charge |
Practice
Ionic compounds have high melting points because:
Breaking the many strong ionic attractions in the lattice needs a great deal of energy.
Practice
An ionic compound conducts electricity when:
When molten or in solution the ions are free to move and carry charge; when solid they are fixed.
You've got it
Key idea
- ionic compounds form a giant lattice of alternating + and − ions (not molecules)
- high melting points — strong attraction needs much energy
- conducts only when molten/aqueous (ions free to move), not when solid