CAIE A Level Chemistry 9701 · The Periodic Table: chemical periodicity
The table shows the ionic radii of some Period 3 ions.
| Ion | Ionic radius / nm |
|---|---|
| Na⁺ | 0.095 |
| Mg²⁺ | 0.065 |
| Al³⁺ | 0.050 |
| Si⁴⁺ | 0.041 |
| P³⁻ | 0.212 |
| S²⁻ | 0.184 |
| Cl⁻ | 0.181 |
Suggest why the ionic radius of the positive ions decreases from Na⁺ to Si⁴⁺, and why the negative ions are so much larger than the positive ions.
6 marks, so the mark scheme is looking for about 6 separate creditworthy points. Making the same point twice in different words earns it once.
Suggest means: Apply what you know to an unfamiliar situation. There may be more than one acceptable answer. Reason from the principle you have learned to the new context, and say which principle you are using.
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