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

How does the structure of metals contribute to their electrical conductivity?

1. By hosting numerous free ions

2. Through fixed atoms that do not allow movement

3. By allowing delocalised electrons to move freely

4. Via polar covalent bonds

The correct answer is: By allowing delocalised electrons to move freely

The structure of metals is characterized by a lattice of positively charged ions surrounded by a sea of delocalised electrons. These delocalised electrons are not tied to any specific atom and can move freely throughout the metal. This movement is crucial when it comes to electrical conductivity, as it allows the metal to conduct an electric current effectively. When an electric potential is applied, these free electrons can flow easily, transferring energy and charge through the material. In contrast, other options highlight features that do not contribute to electrical conductivity in metals. The presence of fixed atoms that do not allow movement would inhibit the flow of charge, and polar covalent bonds, while important in some molecules, do not provide the same degree of mobility for charge carriers as delocalised electrons do. Additionally, while ions can contribute to conductivity in some contexts, the mobility and availability of delocalised electrons are what primarily account for metals' high conductivity.