Final answer:
A molecule exhibits a dipole moment when it has an asymmetrical distribution of charge. The dipole moment is related to the molecular geometry and distribution of charge. When a molecule with a dipole moment is placed in an electric field, it tends to align itself with the electric field.
Step-by-step explanation:
A molecule exhibits a dipole moment when it has an asymmetrical distribution of charge. This means that one side of the molecule has a partial positive charge, while the other side has a partial negative charge. The dipole moment is related to the molecular geometry and distribution of charge in that it depends on the individual bond moments and how these dipoles are arranged in the molecule.
For example, if a molecule has a linear shape with two atoms of different electronegativities, the bond between them will have a dipole moment. However, if the molecule has a symmetrical structure like a tetrahedral shape, the individual bond dipole moments may cancel each other out, resulting in a net dipole moment of zero.
When a molecule with a dipole moment is placed in an electric field, it tends to align itself with the electric field because of its asymmetrical charge distribution.