CAIE A Level Chemistry 9701 · Group 2
The thermal stability of the nitrates and carbonates of the Group 2 elements increases down the group, from magnesium to barium.
Explain this trend in terms of the polarising power of the metal cation and the charge density of the anion. In your answer, include equations for the thermal decomposition of barium nitrate and barium carbonate.
7 marks, so the mark scheme is looking for about 7 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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