A Level Chemistry OCR Practice Exam

What is the principal characteristic of delocalised electrons in a metallic lattice?

1. They are fixed in position within the metal structure.

2. They move freely throughout the entire structure contributing to conductivity.

3. They participate in catalysis exclusively.

4. They create ionic bonds with neighboring positive ions.

The correct answer is: They move freely throughout the entire structure contributing to conductivity.

Delocalised electrons in a metallic lattice are characterized by their ability to move freely throughout the entire structure, which greatly contributes to the conductivity of metals. This mobility allows metals to efficiently conduct electricity, as these delocalised electrons can respond to applied electric fields and carry charge through the metal. Metals have a specific structure where the positive metal ions are surrounded by a ‘sea’ of delocalised electrons. These electrons are not bound to any specific atom; instead, they are spread out over the lattice, providing the metallic bond with its unique properties. This is why metals are typically good conductors of electricity and heat, in contrast to other materials where electrons are more localized and cannot move as freely. The other options do not accurately reflect the nature of delocalised electrons. They are not fixed in position, do not solely participate in catalysis, and do not form ionic bonds, which are instead characteristic of the interactions in ionic compounds.