Covalent Bonds and Their Representations

Sep 1, 2024

Lecture Notes: Covalent Bonds and Their Representations

Overview

  • Atoms can form covalent bonds by sharing electrons.
  • Different methods to represent covalent bonds.

Ionic Bonds Recap

  • Ionic bonds involve transferring electrons from one atom to another.
  • Oppositely charged ions are created and held together by electrostatic forces.
  • Typically occur when one atom has excess electrons and another needs more (e.g., Sodium and Chlorine).

Covalent Bond Formation

  • Occurs between two non-metal elements, such as two chlorine atoms.
  • Atoms share electrons to achieve full outer shells.
  • Example: Each chlorine atom shares one electron, resulting in a shared pair.

Representations of Covalent Bonds

Dot and Cross Diagrams

  • Illustrate shared electrons between atoms.
  • Use dots and crosses to differentiate electron origins.
  • Only the outermost shells are typically drawn, check requirements for full shell drawings.

Displayed Formula

  • Use chemical symbols and lines to denote covalent bonds.
  • Efficient for larger molecules, like glucose.
  • Do not show 3D molecular shapes.

3D Models

  • Represent 3D molecular arrangements.
  • Do not need to predict shapes yet, just recognize them.

Example: Ammonia (NH3)

  • Consists of one nitrogen and three hydrogen atoms.
  • Nitrogen needs three extra electrons, hydrogen needs one each.
  • Dot and Cross: Electrons shared to fill outer shells.
  • Displayed Formula: Lines replace shared electrons.

Types of Covalent Substances

Simple Molecular Substances

  • Small molecules with strong covalent bonds.
  • Weak intermolecular forces between molecules.
  • Examples: Chlorine, Ammonia, Water (H2O), Methane (CH4).

Larger Structures

  • Polymers: Long chains of repeating units (monomers).
    • Used in items like plastic bags and t-shirts.
  • Giant Covalent Structures: Consist of extensive atomic networks.
    • Examples: Silicon dioxide, Diamond, Graphite.
    • Extremely strong due to covalent bonding.

Conclusion

  • Covalent bonds form various substances from small molecules to giant structures.
  • Understanding how to represent these bonds is essential.

Note: Review related videos for more on polymers and giant covalent structures.