General Chemistry: Bonding & Intermolecular Forces
Free MCAT study guide — Chemical and Physical Foundations of Biological Systems
Chemical Bonding
Bond Types
- Ionic: Transfer of electrons (ΔEN > 1.7). Metals + nonmetals. High melting point, conduct when dissolved.
- Covalent: Sharing of electrons (ΔEN < 1.7). Nonmetals. Polar if ΔEN > 0.5.
- Metallic: "Sea of electrons." Conducts electricity, malleable, ductile.
VSEPR and Molecular Geometry
Key Point: Lone pairs compress bond angles. H₂O: 104.5° (not 109.5°), NH₃: 107° (not 109.5°).
Intermolecular Forces
| IMF Type | Strength | Requirement | Example |
|---|---|---|---|
| London dispersion | Weakest | All molecules | He, CH₄ |
| Dipole-dipole | Moderate | Polar molecules | HCl, acetone |
| Hydrogen bonding | Strong | H bonded to F, O, N | H₂O, NH₃, HF |
| Ion-dipole | Strongest | Ions + polar molecules | NaCl in H₂O |
Key Point: IMFs determine boiling point, melting point, viscosity, and surface tension. Stronger IMFs = higher BP.
London forces ∝ polarizability ∝ molecular size and electron count
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