Cambridge O Level Chemistry · Syllabus 5070 · Atoms, Elements and Compounds
Delocalised electron
What is Delocalised electron?
An electron that is not held in a bond between two particular atoms and is free to move through the structure. In graphite each carbon atom is bonded to only three others, so one of its outer electrons is delocalised and can move through the layers, which is why graphite conducts electricity. Metals contain delocalised electrons for the same reason: mobile charge carriers make a substance conduct in the solid state.
This definition is part of the Atoms, Elements and Compounds chapter in Cambridge O Level Chemistry.
Common mistakes with Delocalised electron
- 8. “Anything with a lattice structure conducts electricity.” Repair Conduction needs a mobile charged particle. A metallic lattice has mobile delocalised electrons, so it conducts. An ionic lattice has ions that are fixed until it is molten or dissolved. Diamond has neither, so it does not conduct at all. Taught fully in Lesson 2.4C and Lesson 2.7.
Questions students ask about Delocalised electron
How do you explain the properties of a substance from its structure in an exam answer?
Walk the chain: identify the particles, follow the outer electrons, name the structure, then read the property off the structure. For melting point, say which particles are held together, by which attraction, and how much energy is needed to overcome it. For conductivity, name the mobile charged particle — delocalised electrons in a metal or graphite, mobile ions in a molten or aqueous ionic compound — or state that there is none. Marks are given for each link in the chain, not for the final word alone.