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

How does the structure of metals relate to their conductivity?

1. Positive ions can move freely

2. Delocalised electrons can move and carry charge

3. All atoms are fixed in place

4. Only some metals are conductive

The correct answer is: Delocalised electrons can move and carry charge

The conductivity of metals is closely related to the presence of delocalized electrons within their structure. In metallic bonding, atoms are arranged in a lattice structure where the outermost electrons are not tied to any single atom but are instead free to move throughout the metallic lattice. This phenomenon occurs due to the "sea of electrons" model, where these delocalized electrons are able to flow easily in response to an electric potential, effectively carrying charge through the metal. As a result, when an electric field is applied, these free electrons can drift towards the positive terminal, creating an electric current. This ability for electrons to move freely is what enables metals to conduct electricity so efficiently. The other options do not accurately describe the key reasons behind metallic conductivity. The notion that all atoms are fixed in place contradicts the essential characteristic of conductive metals, which rely on the mobility of their electron sea. Moreover, the statement that only some metals are conductive does not address the fundamental structure and behavior of those that are conductive when they possess delocalized electrons.