Covalent Bonds and Structures

Covalent Bonds Overview

• Non-metals can join together by covalent bonds.
• Covalent bonds involve sharing electrons, resulting in full outer shells.

Types of Covalent Structures

Simple Molecular Substances

• Form small molecules (e.g., chlorine, ammonia).
• Properties:
  • Strong bonds within molecules.
  • Weak intermolecular forces between molecules.
  • Low melting and boiling points (e.g., chlorine boils at -34°C).
  • Do not conduct electricity (no free electrons or charge).

Giant Covalent Structures

• Examples include diamond, graphite, and silicon dioxide (SiO₂).
• Properties:
  • Very strong due to numerous covalent bonds.
  • High melting and boiling points (need to break all covalent bonds).
  • Generally, do not conduct electricity, except graphite.

Intermolecular Forces

• In simple molecules, the more intermolecular forces, the higher the boiling point.
• Boiling points increase down the group in halogens (e.g., chlorine to iodine).
  • Chlorine boils at -34°C, bromine at 59°C, iodine at 184°C.

Important Examples

Diamond and Graphite

• Both are forms of carbon.
• Detailed discussion in another video.

Silicon Dioxide (Silica)

• Comprised of silicon and oxygen in a 1:2 ratio.
• Main component of sand.

Key Takeaways

• Simple molecular substances have weak intermolecular forces and low boiling/melting points.
• Giant covalent structures are strong with high boiling/melting points, generally non-conductive.

Conclusion

• Understand differences in properties and structures between simple molecular substances and giant covalent structures.