2.2.16
HL
ONLY
Hybridization
Mixing atomic orbitals to explain molecular geometry.
Hybridization Types
| Electron Domains | Hybridization | Geometry | Example |
|---|---|---|---|
| 2 | sp | Linear (180°) | CO₂, C₂H₂ |
| 3 | sp² | Trigonal Planar (120°) | BF₃, C₂H₄ |
| 4 | sp³ | Tetrahedral (109.5°) | CH₄, NH₃, H₂O |
Quick Shortcut
Count the electron domains (bonding + lone pairs) around the central atom. Subtract that from 4 to find unhybridized p-orbitals.
- 2 domains → sp (2 unhybridized p → available for 2 π bonds)
- 3 domains → sp² (1 unhybridized p → available for 1 π bond)
- 4 domains → sp³ (0 unhybridized p → no π bonds)
Putting it All Together: Ethene (C₂H₄)
- Each C has 3 electron domains → sp² hybridized.
- The sp² orbitals form 3 σ bonds (2 C–H + 1 C–C).
- The remaining unhybridized p-orbital forms the π bond sideways.
- Result: C=C is 1σ + 1π. Planar geometry. Restricted rotation.