CAIE A Level Chemistry 9701 · The Periodic Table: chemical periodicity
The oxides of the period 3 elements sodium, magnesium, aluminium, phosphorus and sulfur show a range of oxidation numbers. Explain how the oxidation number of the element in each oxide is related to the number of outer shell (valence) electrons it has. In your answer, state the oxidation number of the element in each of the oxides , , , and .
4 marks, so the mark scheme is looking for about 4 separate creditworthy points. Making the same point twice in different words earns it once.
Explain means: Give the reasons or the mechanism: why or how something happens. Link each point to the next with because, so or which means. A list of facts with no links usually loses the reasoning marks.
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