Freeze Lessons: Covalent Bonding

Objectives

• Describe how electrons are shared in covalent bonding.
• Draw diagrams to show covalent bonding with double and triple covalent bonds.

Review of Single Covalent Bonds

• Single covalent bond: a shared pair of electrons.
• Examples: Hydrogen, Chlorine, Hydrogen Chloride, Water, Ammonia, Methane.

Covalent Bonding in Molecules

Oxygen Molecule (O2)

• Formula: O2
• Composition: Two oxygen atoms.
• Electron Configuration: Oxygen atoms have six electrons in the outer energy level.
• Bonding:
  • Each oxygen atom needs two more electrons for a full outer energy level.
  • They overlap their outer energy levels to share two pairs of electrons.
  • Double Covalent Bond: Involves two shared pairs of electrons.
  • Diagrams:
    • Dot and cross
    • Stick diagram: double covalent bond shown as two lines.

Nitrogen Molecule (N2)

• Formula: N2
• Composition: Two nitrogen atoms.
• Electron Configuration: Nitrogen atoms have five electrons in the outer energy level.
• Bonding:
  • Each nitrogen atom needs three more electrons for a full outer energy level.
  • They overlap to share three pairs of electrons.
  • Triple Covalent Bond: Involves three shared pairs of electrons.
  • Diagrams:
    • Dot and cross
    • Stick diagram: triple covalent bond shown as three lines.

Carbon Dioxide (CO2)

• Formula: CO2
• Composition: One carbon atom and two oxygen atoms.
• Electron Configuration:
  • Carbon atom has four electrons in the outer energy level.
  • Oxygen atom has six electrons in the outer energy level.
• Bonding:
  • Carbon atom requires four more electrons; each oxygen requires two more.
  • Carbon atom forms a double covalent bond with each oxygen atom.
  • All atoms achieve a full outer energy level.
  • Diagrams:
    • Dot and cross
    • Stick diagram for carbon dioxide.

Additional Resources

• Practice questions available in the revision workbook linked in the video.

Note: Carbon dioxide is not on the AQA specification but is required for Edexcel students.