10. Covalent Lattices (2025)

Covalent Lattices

Overview

• Topic: Covalent lattices

• Relevant to Year 11 Chemistry.

Recap of Key Ideas

• Valence Electrons: Carbon has 4 valence electrons.

• Covalent Bonds: Carbon can form a maximum of 4 covalent bonds with other atoms.

• Intramolecular Bond Example: Covalent bond.

• Intermolecular Bond Example: Hydrogen bond.

• Strongest Intermolecular Bond: Depends on specific molecules presented.

Learning Intentions

• Understanding: Structure and properties of covalent lattice structures.

Success Criteria

• Differentiate between discrete covalent molecules and giant 3D lattices.

• Explain what an allotrope is with examples (e.g., diamond, graphite).

• Describe differences between covalent network lattices and covalent layer lattices.

• Use chemical structures to explain the properties of these lattices.

Allotropes of Carbon

• Definition: Different forms of the same element with distinct chemical/physical properties.

• Examples include diamond, graphite, charcoal.

Properties Comparison

• Diamond: Hard, non-conductive, high melting/boiling points.

• Graphite: Soft, conductive, high melting points, slippery.

Discrete Molecules

• Types of interactions:

  • Dispersion forces

  • Dipole-dipole bonds

  • Hydrogen bonds

Giant 3D Structures

• Characteristics of solids at room temperature.

• Types:

  • Network lattice

  • Layer lattice

Covalent Network Lattice

• Structure: Each carbon atom is covalently bonded to 4 other carbon atoms.

Properties of Network Lattices

• High boiling and melting points.

• Very hard and brittle.

• Non-conductive of electricity.

Covalent Layer Lattice

• Structure: Each carbon atom is covalently bonded to 3 others, with one delocalized electron.

Properties of Layer Lattices

• High melting point (can sublime).

• Slippery (used in pencils/lubricants).

• Metallic sheen (shiny appearance).

• Conducts electricity due to delocalized electrons.

Giant Chemical Structures

• Examination of the differences between discrete covalent molecules and giant 3D lattices.

Tasks

• Complete notes and exercise questions based on today's lesson.

• Finish the Edrolo quiz and reflect on understanding.

• Utilize success criteria to summarize key ideas.

Review Questions (Key Concepts)

1. Covalent bonds in carbon: Diamond (4), Graphite (3).

2. Sublimation: Solid to gas transition (no liquid phase).

3. Uses for amorphous carbon: Printer toner, ink, rubber reinforcement, pencil lead, charcoal.

4. Properties of diamond and graphite linked to bonding and structure:

   • Diamond: Hard due to strong covalent bonds; non-conductive; good heat conductor.

   • Graphite: Soft due to weak dispersion forces; conductive due to delocalized electrons.