Intermolecular Forces

[nataliefgarcia3I]

Can someone explain how to determine dipole-dipole and london forces?

[305154707]

Dipole dipole moments are forces of attraction between the oppositely charged ends of polar molecules. London forces (or induced-induced dipoles) are when two things are originally non polar, but when placed next to each other, they become polar. It is a short lived interaction caused by a temporary dipole within the atoms involved.

[isarose0]

London dispersion forces are always present between molecules, for polar and non-polar, however they are the only intermolecular forces present for non-polar.

[Danny Zhang 4L]

I believe the main difference to know is that London forces occur in all molecules while dipole-dipole forces only occur in polar molecules.

[Kristy 1F]

Dipole-dipole forces are attractive forces between the positive end of one polar molecule and the negative end of another polar molecule.The London dispersion force is the weakest intermolecular force.
The London dispersion force is a temporary attractive force that results when the electrons in two adjacent atoms occupy positions that make the atoms form temporary dipoles. This force is sometimes called an induced dipole-induced dipole attraction. London forces are the attractive forces that cause nonpolar substances to condense to liquids and to freeze into solids when the temperature is lowered sufficiently.

[404536963]

Non-polar molecules are attracted through London forces and polar molecules are attracted as well, but stronger through dipole-dipole attractions. So to determine, look at the electronegativity of the molecule. Also, size can help determine. Smaller molecules tend to have stronger dipole- dipole forces, and larger molecules tend to have London forces. London forces are temporary, so they tend to be weaker than permanent dipole-dipole forces.

[Ahmed Mahmood 4D]

Determinant factors include strength, molecular size, and electronegativity. London forces are usually weaker. Smaller molecules are primarily dipole-dipole, while the inverse is true for London forces. Greater differences in electronegativity typically indicate dipole-dipole forces.

[nataliefgarcia3I]

Thank you guys so much!