International General Certificate of Secondary Education (IGCSE) Chemistry Practice Exam

How does graphite conduct electricity?

1. Via moving ions in its structure

2. Through delocalised electrons that can move freely

3. By the presence of fixed electrons

4. Through covalent bonds

The correct answer is: Through delocalised electrons that can move freely

Graphite conducts electricity effectively due to the presence of delocalised electrons within its structure. In a graphite crystal, each carbon atom is bonded to three other carbon atoms in a planar arrangement, using three of its four outer-shell electrons to form covalent bonds. The fourth electron from each carbon atom is free to move, creating a sea of delocalised electrons that are not bound to any specific atom. These delocalised electrons can move freely throughout the layers of graphite, allowing for electrical conductivity. The structure of graphite also consists of layers held together by weak van der Waals forces, which allows layers to slide over each other. This layered structure enhances the movement of delocalised electrons and contributes to the overall conductivity. In contrast, conductivity via moving ions would be typical in ionic compounds, and fixed electrons do not contribute to conductivity at all. Covalent bonds also do not conduct electricity, as they do not allow for the free movement of charge. Hence, the ability of graphite to conduct electricity is due to its delocalised electrons.