If you look at the diagram carefully, you will see that the sodium ions and chloride ions alternate with each other in each of the three dimensions. That is different from, say, a water molecule which always contains exactly 2 hydrogen atoms and one oxygen atom - never more and never less.Ī small representative bit of a sodium chloride lattice looks like this:
There could be billions of sodium ions and chloride ions packed together, or trillions, or whatever - it simply depends how big the crystal is. It means that you can't state exactly how many ions there are. You should be clear that giant in this context doesn't just mean very large. So sodium chloride (and any other ionic compound) is described as having a giant ionic structure. Compounds like this consist of a giant (endlessly repeating) lattice of ions. Sodium chloride is taken as a typical ionic compound. How the ions are arranged in sodium chloride The structure of a typical ionic solid - sodium chloride It isn't important for understanding this page, however. Note: If you need to revise how ionic bonding arises, then you might like to follow this link.
It also explains why caesium chloride has a different structure from sodium chloride even though sodium and caesium are both in Group 1 of the Periodic Table. 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 behaviour.
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