Metallic bonding and types of crystal structureAQA A-Level Chemistry: Subtopic test

1. 1
   A technician is testing four unlabelled solids at room temperature. Solid W conducts electricity, is malleable and melts at 650 °C. Solid X does not conduct as a solid, conducts when molten and melts at 801 °C. Solid Y does not conduct in any state and melts at 114 °C. Solid Z is very hard, does not conduct and melts above 3500 °C.

   (a)

   Which type of structure does solid Y most probably have?

   [1 mark]

   • AGiant ionic lattice
   • BSimple molecular
   • CMacromolecular (giant covalent)
   • DGiant metallic lattice

   (b)

   Which of the following could be solid Z?

   [1 mark]

   • AMagnesium
   • BSodium chloride
   • CIodine
   • DDiamond

   (c)

   Explain why solid X conducts electricity when molten but not when solid.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A student compares sodium, which melts at 98 °C, with magnesium, which melts at 650 °C. Both metals conduct electricity as solids and both can be hammered into shape.

   (a)

   Which particles are present in solid sodium?

   [1 mark]

   • ANa⁺ ions and delocalised electrons
   • BNa⁺ ions and Na⁻ ions
   • CNeutral Na₂ molecules
   • DNa atoms held by shared pairs of electrons

   (b)

   Which statement best explains why magnesium has a higher melting point than sodium?

   [1 mark]

   • AMagnesium ions are larger, so the lattice is more stable
   • BMagnesium atoms have a greater relative atomic mass, so they vibrate more slowly
   • CMagnesium ions have a higher charge and each atom releases two delocalised electrons, so the attraction is stronger
   • DMagnesium has stronger induced dipole-dipole forces between its atoms

   (c)

   Explain why sodium can be hammered into shape without breaking.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   Graphite and diamond are both forms of carbon. Graphite is used as electrodes and as the 'lead' in pencils, which leave a mark because layers rub off onto paper. Diamond is used on the cutting edges of drill bits.

   (a)

   Explain why graphite conducts electricity but diamond does not.

   [3 marks]

   (b)

   Explain why diamond is suitable for cutting while graphite is suitable as a pencil lead.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A chemist is studying four substances at room temperature: sodium chloride (melting point 801 °C, brittle), magnesium (melting point 650 °C, boiling point 1090 °C, conducts as a solid), iodine (melting point 114 °C, does not conduct) and ice (melting point 0 °C). She wants to explain their properties from their structures.

   (a)

   Compare the structure and bonding of sodium chloride and iodine, and explain why they differ in melting point and in electrical conductivity.

   [6 marks]

   (b)

   Magnesium is heated steadily from 25 °C until it becomes a gas. Explain, in terms of particles and bonding, the energy changes that occur, including why the temperature stays constant while it melts and why boiling needs far more energy than melting.

   [6 marks]

   Total for question 4: 12 marks

End of questions