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.