Atoms linked by covalent bonds throughout, such as diamond and quartz, give extreme hardness and melting points.
Practise Bonding & Molecular Structure All Bonding & Molecular Structure topics
Covalent network solids consist of atoms linked by strong covalent bonds in a continuous three-dimensional network throughout the crystal. There are no discrete molecules, so melting requires breaking covalent bonds rather than overcoming weak intermolecular forces. This gives these solids extreme hardness, very high melting points and typically poor electrical conductivity, since electrons are localized in bonds. Examples include diamond, quartz and silicon carbide. Their properties follow from the strength and directionality of the bonding network. Graphite is a notable exception because it conducts electricity.
Key ideas: Examples to remember: diamond (carbon), silicon, SiC, SiO2, BN and Al2O3 types. Mohs hardness diamond 10. Melting involves breaking covalent bonds, so melting points are above 1500 C: SiO2 about 1710 C, SiC sublimes near 2700 C. Insoluble in common solvents and non-conducting except for graphite and semiconductors like silicon.
Common mistakes and connections: Students sometimes write a molecular formula such as SiO2 as a discrete molecule: CO2 is a gas of molecules, while SiO2 is a network, which explains their huge difference. Another error is saying that all network solids are insulators. Links to allotropes of carbon, semiconductors, hardness and glass structure.
Atoms bonded in a continuous covalent network require huge energy to separate, so melting points are very high, reaching about 3550 C for diamond. The interactive lesson shows this as a live animation or chart.
Quartz, SiO2, melts at about 1700 degrees Celsius because its three-dimensional network of Si-O bonds must be broken.
Atoms linked by covalent bonds throughout, such as diamond and quartz, give extreme hardness and melting points.
Covalent Network Solids is a intermediate topic in Bonding & Molecular Structure. It builds on the vocabulary of beginner topics in this area.
Study these earlier topics in Bonding & Molecular Structure first: Boiling Point and Intermolecular Forces, Intramolecular Hydrogen Bonding, Water's Anomalous Properties.
The next topics in Bonding & Molecular Structure are Molecular Solids and Ionic Solids.
Yes. The interactive lesson includes a self-check question on Covalent Network Solids, and the Bonding & Molecular Structure quiz draws on every topic in this area.
Covalent Network Solids is topic 79 of 104 in Bonding & Molecular Structure.