Brainlag PlusDiamond, graphite and silicon dioxide, then graphene, fullerenes and nanotubes, and how structure decides hardness, melting point and conduction.
Every atom bonded to its neighbours
In a giant covalent structure there are no separate molecules: every atom is joined to others by strong covalent bonds, on and on through the whole solid.
Melting means breaking huge numbers of these bonds, so the melting points are very high (diamond about 3550 °C, silicon dioxide about 1710 °C).
- Diamond: each carbon bonded to four others in a rigid 3D network. Very hard, very high melting point, does not conduct (no free electrons).
- Silicon dioxide (silica, sand): each silicon bonded to four oxygens, each oxygen to two silicons.
- Graphite: each carbon bonded to three others in flat layers of hexagonal rings.
The rest of this lesson and its 9 practice questions are in Plus.
Screen 1 of 5, free to read.
- 9 exam-style questions, marked as you go, each with a worked solution
- Anything you get wrong is saved to your flashcards