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S1.1 - Introduction to the particulate nature of matter S1.2 - The nuclear atom S1.3 - Electron configurations S1.4 - Counting particles by mass - The mole S1.5 - Ideal gases S2.1 - The ionic model S2.2 - The covalent model S2.3 - The metallic model S2.4 - From models to materials S3.1 - The periodic table - Classification of elements S3.2 - Functional groups - Classification of organic compounds R1.1 - Measuring enthalpy changes R1.2 - Energy cycles in reactions R1.3 - Energy from fuels R1.4 - Entropy and spontaneity AHL R2.1 - How much? The amount of chemical change R2.2 - How fast? The rate of chemical change R2.3 - How far? The extent of chemical change R3.1 - Proton transfer reactions R3.2 - Electron transfer reactions R3.3 - Electron sharing reactions R3.4 - Electron-pair sharing reactions

S2.2 - The covalent model

2.2.1 Covalent Bonds and Lewis Formulas 2.2.2 Bond Types 2.2.3 Co-coordination (Dative) Bonds 2.2.4 VSEPR Shapes of Molecules 2.2.5 Electronegativity and Bond Polarity 2.2.6 Polarity and Dipole Moments 2.2.7 Covalent Network Structures and Allotropes 2.2.8 Intermolecular Forces 2.2.9 Physical Properties of Covalent Substances 2.2.10 Chromatography and Intermolecular Forces 2.2.11 Resonance Structures (AHL) 2.2.12 Benzene and Resonance (AHL) 2.2.13 Expanded Octet and VSEPR (AHL) 2.2.14 Formal Charge (AHL) 2.2.15 Sigma and Pi Bonds (AHL) 2.2.16 Hybridization (AHL)

Molecular Polarity and Dipole Moments

Specification Reference S2.2.6

Quick Notes

  • A molecule is polar if it has a net dipole moment.
  • Molecular polarity depends on the polarity of individual bonds and the shape (geometry) of the molecule.
  • Even if a molecule has polar bonds, the dipoles may cancel depending on geometry.
  • Non-polar molecules:
    • No polar bonds present
    • Or molecule has a symmetrical shape where bond dipoles cancel
  • Polar molecules:
    • Asymmetric shape
    • Or dipoles that don’t cancel

Full Notes

What Determines Molecular Polarity?

A molecule can be polar or non-polar, depending on whether it contains polar bonds and the molecule’s symmetry.

Non-polar molecules have no permanent dipole

If polar bonds are arranged symmetrically, dipoles cancel out and the molecule is non-polar.

IB Chemistry diagram showing non-polar molecules with symmetrical bond dipoles cancelling out.

Example: CO2

Each C=O bond is polar, but the molecule is linear, so dipoles cancel. No overall dipole = non-polar molecule.

Example: CCl4 (Tetrachloromethane)

Each C–Cl bond is polar, but tetrahedral shape means dipoles cancel. CCl4 is non-polar despite having polar bonds.

Polar molecules have a permanent dipole

If dipoles do not cancel due to asymmetry, the molecule is polar.

IB Chemistry diagram showing polar molecules with asymmetric shapes where dipoles do not cancel.

Example: H2O

O–H bonds are polar and form a bent shape (104.5°). Dipoles do not cancel meaning water is polar.

Example: CHCl3 (Chloroform)

The C–H and C–Cl bonds have different polarities. Dipoles do not cancel meaning CHCl3 is polar.

How to Deduce Molecular Polarity

Deciding whether a molecule is polar or non-polar can be difficult – even if it contains polar bonds!

Follow this method:

Summary