Edexcel A-Level Chemistry AS 3.6 The Effects of Ionic Radius and Ionic Charge on the Strength of Ionic Bonding Questions

Practise comparing ionic bond strength using ionic radius and charge, often through melting temperatures or ion-pair choices.

Exam points

compare bond strength by linking smaller ionic radii to stronger electrostatic attraction
explain melting temperature differences using attraction between specified ions

[Maximum number: 2]

This question is about magnesium, magnesium oxide and magnesium sulfate.

Magnesium oxide and magnesium sulfate are ionic compounds.

The melting temperatures of magnesium oxide and magnesium sulfate are $2852^{\circ} \mathrm{C}$ and $1124^{\circ} \mathrm{C}$ respectively.

Explain why the melting temperature of magnesium oxide is significantly higher than that of magnesium sulfate.

An answer that makes reference to the following points:

- oxide/ $\mathrm{O}^{2-}$ smaller than sulfate/ $\mathrm{SO}_{4}{ }^{2-}$

- stronger (electrostatic) attraction between the ( $\mathrm{Mg}^{2+}$ and $\mathrm{O}^{2-}$ ) ions

Allow just the oxide is smaller or vice versa Do not award comparison with sulfur or sulfide

Allow stronger ionic bond

Allow more energy required to break the ionic bond

Allow reverse argument Ignore reference to lattice energy Ignore reference to distortion/polarisation Any reference to intermolecular forces /covalent bond/molecular structure score 0

(2)

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Edexcel A-Level Chemistry AS 3.6 The Effects of Ionic Radius and Ionic Charge on the Strength of Ionic Bonding Questions question 1