Unit 12B - Molecular Polarity - Intermolecular Forces - AP Chemistry

polar molecule

a molecule that can be turned so that it has opposite partial charges on opposite sides

in order to be polar, a molecule must have…

1. one or more polar bonds

2. an “axis of asymmetry” meaning a way to view the molecule so that there is more partial positive charge on one side (relative to the central atom), and partial negative charge on the opposite side

dipole moment

a measure of how strongly a dipole will react to an external field, expressed as the moment if inertia caused by a par of charges (+q and -q) separated by a distance d

large dipole moment

indicates a more polar molecule

• stronger (partial) charges and/or greater distance between the charges

dipole moment = qd

momentary dipoles

a random dipole moment that can theoretically form around any sign atom due to random, uneven distribution of electrons around an atoms nucleus

induced dipoles

occur when an instantaneous dipole occurs, and forms an attractive force by inducing a dipole on a neighboring atom, very weak partial charges