The physical properties of ionic substances
3 marks · EasyThe table shows part of the arrangement of ions around a sodium ion in sodium chloride:
| Ion | Count | Distance from central sodium ion (pm) |
|---|---|---|
| Chloride ion | 6 | 280 |
| Sodium ion | 12 | 400 |
| Chloride ion | 8 | 490 |
What type of lattice is formed by sodium chloride?
How many chloride ions are nearest to each sodium ion?
Describe how the pattern of ions continues in the lattice.
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(a) Giant ionic lattice.
(b) 6 chloride ions.
(c) The same arrangement of sodium and chloride ions repeats in all directions throughout the lattice.
Common mistakes: 12 chloride ions nearest (wrong distance); It's a molecule
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Marking points
B1 (a) · 1 mark · Names the lattice as a 'giant ionic lattice'
B1 (b) · 1 mark · States there are 6 chloride ions nearest each sodium ion
B1 (c) · 1 mark · States the pattern repeats throughout the lattice
Worked solution
a) Sodium chloride forms a giant ionic lattice. b) There are 6 chloride ions nearest each sodium ion (at 280 pm distance). c) This pattern repeats itself in all directions, forming the giant lattice.