Metallic bondingEdexcel International A Level Chemistry: Subtopic test

1. 1
   A student connects a strip of magnesium ribbon and, separately, a lump of solid sulfur into a simple circuit containing a lamp and a 6 V battery. The lamp lights when the magnesium is in the circuit but stays off when the sulfur is in the circuit.

   (a)

   How many delocalised electrons does each magnesium atom contribute to the metallic lattice?

   [1 mark]

   • A0
   • B1
   • C2
   • D3

   (b)

   When the 6 V battery is connected across the magnesium ribbon, which particles carry the current through the metal?

   [1 mark]

   • ADelocalised electrons moving through the lattice
   • BMg²⁺ ions moving towards the negative terminal
   • CMg atoms moving towards the positive terminal
   • DElectrons moving between pairs of atoms along covalent bonds

   (c)

   Explain why magnesium conducts electricity but sulfur does not.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   Copper is hammered into sheets for roofing and drawn into thin wires for cables. Pure copper melts at 1085 °C, and a molten sample of copper can be poured and cast into moulds.

   (a)

   Which statement describes the structure of solid copper?

   [1 mark]

   • AAtoms held together by shared pairs of electrons
   • BPositive ions and negative ions in a regular lattice
   • CSeparate Cu₂ molecules attracted by weak forces
   • DA regular lattice of positive ions surrounded by delocalised electrons

   (b)

   Which statement about copper melting at 1085 °C is correct?

   [1 mark]

   • AMetallic bonding is completely broken and the copper ions are separated from the electrons
   • BThe regular lattice breaks down, but the ions and delocalised electrons are still attracted to each other in the liquid
   • CThe delocalised electrons are all lost from the metal
   • DThe copper ions gain electrons and become copper atoms

   (c)

   Explain, in terms of its bonding, why copper can be hammered into sheets without breaking.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   Aluminium is used for overhead power cables because it has a low density and conducts electricity well. A cable is made from solid aluminium, which melts at 660 °C.

   (a)

   Describe the structure of, and bonding in, solid aluminium.

   [3 marks]

   (b)

   Use this structure to explain why aluminium conducts electricity and why it has a high melting temperature.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A data book gives these melting temperatures: lithium 181 °C, sodium 98 °C, potassium 63 °C, calcium 842 °C, magnesium 650 °C and aluminium 660 °C. In each metal the atoms release their outer electrons into a lattice of positive ions: Group 1 atoms release one electron, calcium and magnesium two, and aluminium three.

   (a)

   Explain why the melting temperature falls from lithium to potassium, and why calcium melts at a much higher temperature than potassium.

   [6 marks]

   (b)

   Explain why the melting temperature increases from sodium to magnesium to aluminium.

   [6 marks]

   Total for question 4: 12 marks

End of questions