Question 1: Define delocalised electrons in the context of metallic bonding.

Answer: Delocalised electrons are free-moving electrons that are not attached to any specific atom but are shared across a lattice of metal atoms, allowing electrical conductivity and malleability.

Question 2: Explain how the presence of delocalised electrons affects the electrical conductivity of metals.

Answer: Delocalised electrons move freely throughout the metal lattice, enabling the flow of electric charge and thus giving metals their high electrical conductivity.

Question 3: Describe the mechanism by which metallic bonds hold metal atoms together.

Answer: Metallic bonds involve a lattice of positive metal ions surrounded by a 'sea' of delocalised electrons, which attract the ions and hold them together through electrostatic forces.

Question 4: Calculate the number of delocalised electrons contributed by 2 moles of aluminium atoms (Al). Atomic number of Al is 13.

Answer: 26

Question 5: A sample of copper contains 0.5 mol of atoms. How many delocalised electrons are contributed in total, assuming each atom contributes one free electron?

Answer: 0.5

Question 6: Design a simple practical experiment to demonstrate the presence of delocalised electrons in a metal wire.

Answer: One possible experiment involves passing an electric current through a metal wire and demonstrating its conductivity. Students should note the importance of safety precautions such as using appropriate voltage levels, insulating the wire, and ensuring proper circuit connections to safely observe electrical flow, which is enabled by delocalised electrons.

Question 7: Identify the variables in an experiment designed to test the conductivity of different metals and explain why controlling variables is important.

Answer: Variables include the type of metal, length and thickness of the wire, and voltage applied. Controlling these ensures that the results are due to differences in metallic bonding and delocalised electrons, not other factors.

Question 8: Interpret the following scenario: A student measures the electrical resistance of different metal wires. Copper has the lowest resistance, followed by aluminium, then iron. Explain this trend based on delocalised electrons.

Answer: Copper has more delocalised electrons per atom and a more free electron sea, which reduces resistance. Aluminium also has delocalised electrons but fewer than copper, and iron has fewer, resulting in higher resistance.

Question 9: In the context of metallic bonding, explain why metals are malleable and ductile.

Answer: The sea of delocalised electrons allows metal ions to slide past each other without breaking the bond, making metals malleable and ductile.

Question 10: Apply your understanding of delocalised electrons to explain how metals are used in electrical wiring and why they are suitable materials.

Answer: Metals contain delocalised electrons that enable high electrical conductivity, making them ideal for wiring. Their malleability and ductility also allow easy shaping into wires, and their resistance to corrosion in many cases extends their utility in electrical applications.