Types of Intermolecular Forces
This weakest IMF is present in all molecules and becomes stronger for very large molecules.
What are London dispersion forces (or dispersion forces)?
A molecule that has polar bonds and is asymmetrical, leading to a net dipole.
What is a polar molecule?
The temperature at which a liquid boils and turns to vapor — higher values usually indicate stronger IMFs.
What is boiling point?
These attractions occur between permanent dipoles in polar molecules.
What are dipole–dipole interactions?
A molecule with no polar bonds or a symmetrical arrangement so bond dipoles cancel
What is a nonpolar molecule?
The temperature at which a solid becomes a liquid — higher values usually indicate stronger IMFs
What is melting point?
The strongest IMF found when hydrogen is bonded to fluorine, oxygen, or nitrogen.
What is hydrogen bonding?
Term meaning “equal forces acting on the central atom so charges cancel.”
What is symmetrical?
Specific groups of atoms that appear often in molecules and are polar.
What is polar functional group?
The general term for forces that hold molecules to each other caused by electrostatic attraction between partial charges.
What are intermolecular forces?
Uneven forces acting on the central atom, bond polarities do not cancel out, leaving the molecule with a positive side and a negative side (making it polar)
What is asymmetrical?
On the lab slide, this property is used to compare how easily pigments travel on chromatography paper and relates to polarity.
What is Rf (retention factor) or chromatography retention?
The IMF that dominates nonpolar substances and can increase with molecular size/shape.
What are London dispersion forces (LDF)?
The arrow used to show bond polarity that points toward the more electronegative atom.
What is a dipole arrow (or dipole moment arrow)?
The reason hexane typically has a lower boiling point than water based on IMF evidence.
What are weaker intermolecular forces (hexane: mostly dispersion) compared to water’s hydrogen bonding?