CAIE A Level Chemistry 9701 · The Periodic Table: chemical periodicity
An unknown element X is in Period 3 of the Periodic Table. Its oxide, , is a solid at room temperature and dissolves in water to form a solution of pH 4. X reacts with chlorine to form a chloride with the formula , which is a liquid at room temperature.
Explain what these observations suggest about the position of X in Period 3 and the nature of 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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