1. Drawing Lewis Structures
Arrange the element symbols.
Central atoms are generally those with the highest bonding capacity.
Carbon atoms are always central atoms
Hydrogen atoms are always peripheral atoms
Add up the number of valence electrons from all atoms.
For polyatomic ions, add one electron for each negative charge and subtract one for each positive charge.
Draw a skeleton structure with atoms attached by single bonds.
Complete the octets of peripheral atoms.
Place extra electrons on the central atom.
If the central atom doesn’t have an octet, try forming multiple bonds by moving lone pairs.

2. Quantum Mechanics and Bonding

3. QM to Explain Ionic Bonds
Transfer of electron from one orbital to another

4. QM to Explain Covalent Bonds
In grade 11 you noticed exceptions to the octet rule for molecular compounds
A more complex understanding than simple Lewis structures is required
Valence Bond Theory

5. Valence Bond Theory
A covalent bond forms when the atomic orbitals of 2 atoms overlap to share a common region in space
The region of overlap can contain a maximum of 2 electrons with opposite spins (Pauli exclusion principle)
The greater the overlap, the stronger the bond.
Shape of overlap depends on the shape and orientation of orbitals involved
Orbital hybridization occurs when orbitals overlap and combine to form new orbitals

6. Single Bonds End-to-end overlap of orbitals, called sigma (σ) bonds
Examples H2 HF F2

7. Hybridization ExamplesBe B C P S Br Xe

9. Double and Triple Bonds
Side-by-side overlap of orbitals, called pi (π) bonds

10. Practice
Valence Bond Theory Worksheet
P. 232 #1-5
P. 235 #8-14