# Bond polarity and dipole moment

A bond is polar when electrons are shared unequally, giving one end a partial negative charge (δ−) and the other a partial positive charge (δ+). A molecule is polar if its bond dipoles do not cancel.

Chemistry (university) · Part 02: Chemical bonding and molecular shape · Card 6 of 9 · Last updated 2026-10-19

## Analogy

Two people pulling a rope in different directions. If the pulls cancel, the box doesn't move. If not, it slides.

## Example

**CO₂ vs H₂O**

CO₂ is linear, dipoles opposite: cancel.
H₂O is bent, dipoles add up.
So CO₂ is nonpolar, H₂O is polar.

## In practice

Water is polar and dissolves salt. Carbon dioxide has polar bonds but is nonpolar overall because its dipoles cancel.

## Practice

### Flashcards

- **Why is CO₂ nonpolar although C=O bonds are polar?** It is linear, so the two bond dipoles point opposite ways and cancel.

### Interview questions

**Use VSEPR to predict the shape and polarity of SO₂ and CO₂.**

- SO₂ has three groups: two bonds and one lone pair, bent
- CO₂ has two groups, linear
- SO₂ dipoles do not cancel, so polar
- CO₂ dipoles cancel, so nonpolar

## Questions people ask

### Can a molecule with polar bonds be nonpolar?

Yes. If the molecule is symmetric, the bond dipoles point in opposite directions and cancel. CO₂, CCl₄ and BF₃ all have polar bonds but are nonpolar overall. Shape matters as much as the bonds themselves, so always check the geometry before calling a molecule polar.

### How is dipole moment measured?

Dipole moment is charge times distance, measured in debye (D). It can be found by seeing how a substance behaves in an electric field. Water has a dipole moment of about 1.85 D, while symmetric molecules such as CO₂ have a measured value of zero.

## Related concepts

- [VSEPR theory](https://studyvisually.com/learn/science/chemistry-university/chemistry-university-part-2/chemistry-university-part-2-concept-7)
- [Hybridization](https://studyvisually.com/learn/science/chemistry-university/chemistry-university-part-2/chemistry-university-part-2-concept-8)

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