Section 6.5 – Molecular Geometry, Polarity, and Intermolecular Forces
The properties of molecules depend on the _____________________ and the ____________
______________________, the 3-dimensional arrangement of the atoms in space.
Molecular Polarity is the __________________ distribution of molecular charge, and it is determined by the
____________________ of each bond, along with the ________________ of the molecule.
Molecular Polarity and Symmetry
____________________ lines of symmetry  __________________molecule; electrons distributed symmetrically
Only __________________ of symmetry  ____________________ molecule; asymmetrical electron distribution
creates a _________________________
A dipole is created by __________________________________ charges that are separated by a
________________________________
We show a dipole using an _____________________ pointing towards the more
______________________________________ atom
______________ indicates the partial positive charge, and ______________ indicates the partial negative charge
Identify the polar molecules, and indicate the dipole…
H-H
H-Cl
Cl-Cl
Other examples:
Dipoles give each molecule ___________________________ that can be attracted to each other.
As the electronegativity difference _______________, attractive force strength increases =
_______________________________
Intermolecular Forces
These are the forces of attraction that occur _____________________
molecules. They vary in strength but are generally
___________________than regular bonding (ionic, covalent, or metallic).
Intermolecular Forces are responsible for holding molecules together in the
____________ and __________________ phase
Caused by the attraction of the ________end of one molecule to the ________ end of another molecule
Melting and Boiling Points are a measure of the force of attraction between



molecules in _______________________ compounds
ions in ____________________ compounds
and between _________________________ in metals
The higher the boiling point, the stronger the forces ________________________ particles.
3 Types of Intermolecular Forces
1. ____________________________________ Forces
2. _______________________ bonding (special case of D-D)
3. __________________________________________ Forces
Dipole Force
The strongest intermolecular forces exist between _______________________
molecules.
The δ+ end of one molecule is attracted to the δ- end of another molecule.
Dipole-dipole forces are the forces of attraction between polar molecules.
Example: Which is the stronger dipole-dipole force?
bp for F2 is -188°C
bp for HF is 20°C
bp for HCl is -85°C
Induced Dipoles
The electrons of a nonpolar molecule can be ________________________ attracted
by a polar molecule.
This is ___________________________ than a regular dipole-dipole force.
Hydrogen Bonding
A very special type of ___________________________________ force in which a hydrogen atom that is bonded to a
highly electronegative atom is attracted to an unshared pair of electrons of another molecule.
Hydrogen Bondingo nly happens in molecules where H is bonded to ____________________________
Explains High bp’s of Some Compounds
Gives the H atom a _____________________, and it’s small size allows it to come very close to the unshared pair of
electrons on an adjacent molecule.
Explains properties of water
High surface tension
Why ice floats on water
Extremely Important in Biochemistry. Why?
London Dispersion Forces
This is a _________________attractive force resulting from electron motion
and the creation of an _________________________________ dipole.
Important for ____________________ and nonpolar molecules.
London Dispersion forces act between _______________ atoms and molecules
However, dispersion forces are ____________________________ than dipoledipole forces
Dispersion forces are the _________________ forces acting among ________________ atoms, and
____________________________ molecules.
Dispersion forces increase with the _________________________________________ in the interacting atoms or
molecules and increase with increasing _______________________________________________.
Recall the bonding lab and evaporation rates…
Explain why pentane and hexane evaporated quickly, but the other substances did not.
Explain why pentane evaporated more quickly than hexane.