Editing Chemical polarity (section)

== Predicting molecule polarity ==

{|class="wikitable"
|-
!
! Formula
! Description
! Example
! Name
! Dipole moment
|-
! rowspan=5 | Polar
| AB
| Linear molecules
| CO
| [[Carbon monoxide]]
| 0.112
|-
| HA<sub>''x''</sub>
| Molecules with a single H
| HF
| [[Hydrogen fluoride]]
| 1.86
|-
| A<sub>''x''</sub>OH
| Molecules with an OH at one end
| C<sub>2</sub>H<sub>5</sub>OH
| [[Ethanol]]
| 1.69
|-
| O<sub>''x''</sub>A<sub>''y''</sub>
| Molecules with an O at one end
| H<sub>2</sub>O
| [[Properties of water|Water]]
| 1.85
|-
| N<sub>''x''</sub>A<sub>''y''</sub>
| Molecules with an N at one end
| NH<sub>3</sub>
| [[Ammonia]]
| 1.42
|-
! rowspan=3 | Nonpolar
| A<sub>2</sub>
| [[Diatomic molecule]]s of the same element
| O<sub>2</sub>
| [[Dioxygen]]
| 0.0
|-
| C<sub>''x''</sub>A<sub>''y''</sub>
| Most hydrocarbon compounds
| C<sub>3</sub>H<sub>8</sub>
| [[Propane]]
| 0.083
|-
| C<sub>''x''</sub>A<sub>''y''</sub>
| Hydrocarbon with [[center of inversion]]
| C<sub>4</sub>H<sub>10</sub>
| [[Butane]]
| 0.0
|}

Determining the [[Point groups in three dimensions|point group]] is a useful way to predict polarity of a molecule. In general, a molecule will not possess dipole moment if the individual bond dipole moments of the molecule cancel each other out. This is because dipole moments are [[euclidean vector]] quantities with magnitude and direction, and a two equal vectors that oppose each other will cancel out.

Any molecule with a centre of inversion ("i") or a horizontal mirror plane ("σ<sub>h</sub>") will not possess dipole moments. 
Likewise, a molecule with more than one C<sub>''n''</sub> axis of rotation will not possess a dipole moment because dipole moments cannot lie in more than one [[dimension]]. As a consequence of that constraint, all molecules with [[Schoenflies_notation#Point_groups|dihedral symmetry]] (D<sub>''n''</sub>)  will not have a dipole moment because, by definition, D point groups have two or multiple C<sub>''n''</sub> axes.

Since C<sub>1</sub>, C<sub>s</sub>,C<sub>∞h</sub> C<sub>''n''</sub> and C<sub>''n''v</sub> [[Point groups in three dimensions|point groups]] do not have a centre of inversion, horizontal mirror planes or multiple C<sub>''n''</sub> axis, molecules in one of those point groups will have dipole moment.