A Level Chemistry 2017 Paper 1 Question 9 Solution - Exclusive

In this exclusive video we want to discuss the suggested solution for A Levels Chemistry (H2 Chemistry) 2017 Paper 1 Question 9.

Let Chemistry Guru, Singapore's top JC Chemistry tuition centre, guide you through this question.

2017 A Level H2 Chemistry Paper 1 Qn9 Question

Polarising ability or polarising power is a concept commonly discussed in the topics Periodicity, Group 2 metals as well as Chemical Bonding.

Polarising power is the ability of a metal cation to distort the electron cloud of neighbouring electron clouds.

It is related to the metal cation's charge density, which is in turn related to its charge over size.

When a metal cation has a high charge and small size, its charge density and polarising power will be high, and it will be able to distort the electron cloud of a neighbouring anion to a greater extent.

2017 A Level H2 Chemistry Paper 1 Qn9 polarising power and charge density

In the case of metal peroxides, metals with high polarising ability will distort the electron cloud of peroxide O22- to a greater extent, hence the bonds within peroxide is weaker and it decomposes more easily.

That is why metal ions with high polarising ability are less likely to form stable ionic peroxides, as stated in this question.

Finally we just need to compare the 4 options to determine which metal cation has the highest charge density and therefore highest polarising power.

2017 A Level H2 Chemistry Paper 1 Qn9 compare charge density

From the comparison magnesium has the smallest size and highest charge, therefore its charge density and polarising power is the greatest.

So the answer to this question will be C.

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

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