Ionic bonding in magnesium oxide
2 marks · EasyExplain why magnesium oxide has a high melting point. Use your knowledge of ionic bonding in your answer.
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Magnesium oxide has a high melting point because there are strong electrostatic attractions between the oppositely charged Mg^{2+} and O^{2-} ions. A large amount of energy is needed to overcome these ionic bonds.
Must show: references to strong electrostatic forces between ions, recognition that much energy is needed to break these bonds
Also accept: Reference to strong ionic bonds and much energy required
Common mistakes: Reference to covalent bonds; No mention of energy required
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Marking points
M1 · 1 mark · Explains that there are strong electrostatic forces/bonds between Mg^{2+} and O^{2-} ions in the lattice.
A1 · 1 mark · States a large amount of energy is needed to break/overcome these forces.
Worked solution
Magnesium oxide has a high melting point because the strong electrostatic attractions between Mg^{2+} and O^{2-} ions require a large amount of energy to overcome the ionic bonds in the lattice.