The physical properties of sodium chloride
This page explains the relationship between the arrangement of the ions in a typical ionic solid like sodium chloride and its physical properties – melting point, boiling point, brittleness, solubility and electrical behavior. It also explains why cesium chloride has a different structure from sodium chloride even though sodium and cesium are both in Group 1 of the Periodic Table.
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The structure of a typical ionic solid – sodium chloride
Sodium chloride is taken as a typical ionic compound. Compounds like this consist of a giant (endlessly repeating) lattice of ions. So sodium chloride (and any other ionic compound) is described as having a giant ionic structure.
You should be clear that giant in this context does not just mean very large. It means that you can”t state exactly how many ions there are. There could be billions of sodium ions and chloride ions packed together, or trillions, or whatever – it simply depends how big the crystal is. That is different from, say, a water molecule which always contains exactly 2 hydrogen atoms and one oxygen atom – never more and never less. A small representative bit of a sodium chloride lattice looks like this:
The final diagram in this sequence takes a slightly tilted view of the structure so that you can see how the layers build up. These diagrams are quite difficult to draw without it looking as if ions of the same charge are touching each other. They aren”t!