This key facts covers Key Facts to Memorise within Giant Covalent Structures for GCSE Chemistry. Revise Giant Covalent Structures in Bonding & Structure for GCSE Chemistry with 21 exam-style questions and 21 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 7 of 12 in this topic. Use this key facts to connect the idea to the wider topic before moving on to questions and flashcards.
📌 Key Facts to Memorise
- Giant covalent structures = atoms connected by covalent bonds extending in all directions
- No molecules — the whole solid is one giant structure
- Very high melting points — many strong covalent bonds must be broken
- Diamond: 4 bonds per C, very hard, doesn't conduct, transparent
- Graphite: 3 bonds per C, soft layers, CONDUCTS (free electrons), black
- Why graphite conducts: 1 free electron per carbon can move along layers
- Why graphite is soft: weak forces between layers allow them to slide
- Silicon dioxide: similar to diamond structure, very hard, high MP, doesn't conduct
Quick Check: Why do diamond and graphite both have very high melting points, even though graphite is soft?
Both have very high melting points because melting requires breaking the strong covalent bonds within the structure — which takes enormous energy. Graphite is soft because its LAYERS can slide (weak forces between layers), but the covalent bonds within each layer are still very strong. Softness and melting point depend on different forces.
Practice questions for Giant Covalent Structures
Why do giant covalent structures have very high melting points?
Explain why graphite conducts electricity but diamond does not.