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A molecule with a permanent dipole moment is called a polar molecule. See dipole–dipole attractions. Instantaneous dipoles These occur due to chance when electrons happen to be more concentrated in one place than another in a molecule, creating a temporary dipole. These dipoles are smaller in magnitude than permanent dipoles, but still play a ...
The van der Waals forces [4] are usually described as a combination of the London dispersion forces between "instantaneously induced dipoles", [5] Debye forces between permanent dipoles and induced dipoles, and the Keesom force between permanent molecular dipoles whose rotational orientations are dynamically averaged over time.
A molecule with permanent dipole can induce a dipole in a similar neighboring molecule and cause mutual attraction. Debye forces cannot occur between atoms. The forces between induced and permanent dipoles are not as temperature dependent as Keesom interactions because the induced dipole is free to shift and rotate around the polar molecule.
A dipole-induced dipole interaction (Debye force) is due to the approach of a molecule with a permanent dipole to another non-polar molecule with no permanent dipole. This approach causes the electrons of the non-polar molecule to be polarized toward or away from the dipole (or "induce" a dipole) of the approaching molecule. [13]
Interaction energy of an argon dimer.The long-range section is due to London dispersion forces. London dispersion forces (LDF, also known as dispersion forces, London forces, instantaneous dipole–induced dipole forces, fluctuating induced dipole bonds [1] or loosely as van der Waals forces) are a type of intermolecular force acting between atoms and molecules that are normally electrically ...
Debye forces, or dipole–induced dipole interactions, can also play a role in dispersive adhesion. These come about when a nonpolar molecule becomes temporarily polarized due to interaction with a nearby polar molecule. This "induced dipole" in the nonpolar molecule then is attracted to the permanent dipole, yielding a Debye attraction.
The dipoles do not cancel out, resulting in a net dipole. The dipole moment of water depends on its state. In the gas phase the dipole moment is ≈ 1.86 debye (D), [ 11 ] whereas liquid water (≈ 2.95 D) [ 12 ] and ice (≈ 3.09 D) [ 13 ] are higher due to differing hydrogen-bonded environments.
A dipole in such a uniform field may twist and oscillate, but receives no overall net force with no linear acceleration of the dipole. The dipole twists to align with the external field. However, in a non-uniform electric field a dipole may indeed receive a net force since the force on one end of the dipole no longer balances that on the other end.