Lecture Notes: Chemical Bonding

Introduction

• Chemical bonding is similar to Sudoku, requiring knowledge of a few rules.
• Understanding the periodic table is crucial.
  • Groups: 1, 2, transition metals, 3-8 (group 8 has noble gases).
  • Metals are on the left, non-metals on the right.

Types of Bonding

• Ionic Bonding: Metals bond to non-metals.
• Covalent Bonding: Non-metals bond to each other.
• Metallic Bonding: Metals bond to themselves.

Metallic Bonding

• Positive ion lattice surrounded by a sea of delocalized electrons.
• Delocalized electrons allow metals to conduct electricity.

Ionic Bonding

• Atoms desire a full outer shell.
• Metals (e.g., Li, Mg) lose electrons to achieve full shells.
  • Group 1 metals form 1+ ions, Group 2 form 2+ ions.
• Non-metals (e.g., Cl, O) gain electrons.
  • Group 7 non-metals form ions by gaining electrons.
• Ionic compounds form lattices of positive and negative ions, not molecules.

Formulas for Ionic Compounds

• Balance charges to get the formula.
  • Example: Li+ and F- form LiF.
  • Example: Li+ and O2- form Li2O to balance charges.
• Use Roman numerals to indicate ion charge (e.g., Al3+).

Dot and Cross Diagrams

• Illustrate how electrons are transferred between atoms.
• Example: Lithium fluoride shows electron transfer from Li to F.

Special Cases

• Hydrogen can bond both ionically and covalently.
• Molecular ions exist, such as SO4 2- and NO3 -.

Covalent Bonding

• Atoms share electrons to achieve full outer shells.
• Group 7 elements make one bond, Group 6 make two, and so on.
• Example: Two fluorines share electrons.
• Skeletal formulas represent covalent bonds as lines.

Advanced Covalent Structures

• Simple Covalent Structures: Small molecules like methane, CO2.
• Giant Covalent Structures: Large networks like diamond and graphite.
  • Diamond: Tetrahedral grid of carbons.
  • Graphite: Layers of carbon with delocalized electrons between them, allowing layers to slide (used in pencils and lubricants).

Conclusion

• Remember the rules of bonding for exams.
• Draw dot and cross diagrams to visualize bonding.