Covalent Bonds: Formation and Representation

Introduction

• Atoms can form covalent bonds by sharing electrons.
• Different ways to represent covalent bonds.
• Recap of ionic bonds: involves transfer of electrons creating oppositely charged ions.

Covalent Bonding

• Occurs when atoms share electrons.
• Common in non-metal elements, e.g., two chlorine atoms.
• Each atom shares one electron, fulfilling their outer shells.

Drawing Covalent Bonds

Dot and Cross Diagrams

• Use dots for one atom's electrons and crosses for the other's to differentiate.
• Often only the outermost shell is drawn, but sometimes all shells are needed.

Displayed Formula

• Use chemical symbols and lines to represent covalent bonds.
• Easier for drawing large molecules.
• Example: Glucose is represented by a displayed formula.
• Limitation: Does not show the 3D shape of the molecule.

3D Models

• Shows the real-life arrangement of atoms.
• More complex, especially for predicting shapes.
• Required to recognize, not to predict.

Example: Ammonia (NH₃)

• Molecular formula: NH₃
• Structure involves one nitrogen and three hydrogen atoms.
• Process of drawing:
  • Draw outermost shells.
  • Hydrogen needs one extra electron; nitrogen needs three.
  • Each hydrogen shares one electron with nitrogen.
• Dot and cross diagram can be converted to displayed formula.

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).

Polymers

• Large structures with long chains of repeating units (monomers).
• Used in plastics and textiles.

Giant Covalent Structures

• Large structures, e.g., silicon dioxide, diamond, graphite.
• Strong due to continuous covalent bonding.

Conclusion

• Covalent bonds create various types of substances from small molecules to large structures.
• Further understanding of polymers and giant covalent structures is covered in other materials.
• Encouragement to share the video content with friends.