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

Answer: Electrons that are not bound to a specific atom but are free to move throughout the metal lattice, forming a 'sea of electrons'.

Question 2: Explain how delocalized electrons contribute to the electrical conductivity of metals.

Answer: Delocalized electrons are free to move throughout the metal lattice, allowing electric charge to flow easily when a potential difference is applied.

Question 3: Describe the mechanism by which metallic bonds are formed involving delocalized electrons.

Answer: Metal atoms release valence electrons into a shared 'sea of electrons' which are free to move, creating strong electrostatic attractions between the positive metal ions and the delocalized electrons.

Question 1: Calculate the number of delocalized electrons per atom in a metallic lattice of aluminium (Al), given that each atom contributes 3 valence electrons. Assume a simple model where all valence electrons are delocalized.

Answer: 3

Question 2: If a piece of copper (Cu) metal contains 1.5 x 10^21 atoms per cubic centimetre, estimate the total number of delocalized electrons per cubic centimetre, assuming each atom contributes 1 electron to the sea.

Answer: 1.5 x 10^21 electrons

Question 1: Design a simple experiment to investigate how temperature affects the electrical conductivity of a metal. Mention the variables involved and safety precautions.

Answer: A possible experiment involves measuring the resistance of a metal wire at different temperatures using a multimeter. The independent variable is temperature, the dependent variable is resistance. Variables include wire material, length, and voltage applied. Safety precautions include handling hot equipment carefully, avoiding short circuits, and wearing protective gloves.

Question 1: A scientist measures the electrical conductivity of a series of metals and finds that metals with more delocalized electrons tend to have higher conductivity. Explain this trend using your understanding of delocalized electrons.

Answer: Higher numbers of delocalized electrons increase the number of charge carriers available for electrical conduction, thus enhancing the metal's conductivity. Metals with more valence electrons contributing to the sea of electrons typically exhibit better electrical conductivity.

Question 1: Explain why metallic bonds result in high melting points in metals. Include the role of delocalized electrons in your explanation. (6 marks)

Answer: Metallic bonds are strong electrostatic attractions between positive metal ions and the sea of delocalized electrons. The delocalized electrons act as a 'glue', holding the metal ions together tightly. This strong attraction requires a significant amount of energy to break, leading to high melting points in metals.

Question 1: Describe how the concept of delocalized electrons is utilised in the design of electrical conductors used in power transmission lines. Include considerations of material choice and properties.

Answer: Delocalized electrons allow metals like copper and aluminium to conduct electricity efficiently. Their free-moving electrons reduce resistance, enabling high current flow with minimal energy loss. Material choice is based on conductivity, cost, and strength, with copper being common due to its excellent electrical properties.