A Level Chemistry 2017 Paper 1 Question 7 Solution - Exclusive

In this exclusive video we want to discuss the suggested solution for A Levels Chemistry (H2 Chemistry) 2017 Paper 1 Question 7.

Let's take a look at this question.

2017 A Level H2 Chemistry Paper 1 Qn7 Question

Topic tested is on Periodicity of Period 3 Elements, in particular the comparision of electronegativity and atomic radius between magnesium, aluminium, silicon and phosphorus.

The atomic radius can easily be determined from the Data Booklet and we can find that atomic radius decreases from magnesium to phosphorus.

Electronegativity is deduced from the knowledge that fluorine, a Group 17 element, is the most electronegative element.

So the closer the element is to fluorine, the more electronegative it will be.

Therefore phosphorus, which is in Group 15, is closer to Group 17 therefore is more electronegative than magnesium, a Group 2 element.

Putting these two concepts together, the trends and expected graph of electronegativity against atomic radius should look something like this.

2017 A Level H2 Chemistry Paper 1 Qn7 atomic radius and electronegativity trend

So with the trend of atomic radius and electronegativity determined, we can compare the options in the question and choose our best answer.

Out of the 4 options, A and C are eliminated straight away since the shape of the graph is not as expected.

2017 A Level H2 Chemistry Paper 1 Qn7 option A and C

Between options B and D, B is the better answer since there is only a small difference in atomic radius between P (0.110 nm) and Si (0.117 nm).

2017 A Level H2 Chemistry Paper 1 Qn7 option B and D

Check out this video for the full discussion and suggested solution!

Topic: Periodicity, Inorganic Chemistry, A Level Chemistry, Singapore

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