CAIE A Level Chemistry 9701 · Chemical bonding
The Pauling electronegativity values for the elements of Period 3 and Group 2 are shown below.
Period 3: Na 0.9, Mg 1.2, Al 1.5, Si 1.8, P 2.1, S 2.5, Cl 3.0 Group 2: Be 1.5, Mg 1.2, Ca 1.0, Sr 0.9, Ba 0.8
Compare the trend in electronegativity across Period 3 with the trend down Group 2. Explain each trend in terms of nuclear charge, atomic radius and shielding.
5 marks, so the mark scheme is looking for about 5 separate creditworthy points. Making the same point twice in different words earns it once.
Compare means: Give similarities or differences between two things, and say which side each point belongs to. Write each point as a pair, for example: A is X, whereas B is Y. Two separate descriptions rarely earn the marks.
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