1. staircase memory tool! handy moving up this while of IMFs increase
Intermolecular Forces (IMFs)
Forces (not bonds!)BETWEEN molecules
IMFs are much weaker than real bonds
Three important types to know
Have important effects on boiling points
What to Know:
definition of forces
which substances have which forces
how these forces effect boiling points
*** m’c = molecules ***
HYDROGEN “BONDING”
staircase memory tool!
Attraction of m’c to other m’c due to dipole moments of polar m’c that include an H bonded to either an N, O or F. The positive H side of one m’c attracted to negative N, O or F side of a different m’c & vice versa (even stronger than dipole-dipole)
Polar m’c (m’c with dipole moments) that have an H bonded to either an N, O or F have them
These m’c “stick together” even more strongly, and so are harder to boil; this leads to higher boiling points than m’c without hydrogen bonds.
**Please forgive the terrible job we chemists did naming these forces & remember that hydrogen bonds are not really bonds, they’re IMFs!
handy
DIPOLE – DIPOLE FORCES
Types of IMFs
London Dispersion
Dipole-Dipole
Hydrogen Bonding
moving up this
Attraction of m’c to other m’c due to dipole moments of polar m’c. Positive side of one m’c attracted to negative side of a different m’c & vice versa (strong)
Polar m’c (m’c with dipole moments) have them
These m’c “stick together” more, and so are harder to boil; this leads to higher boiling points than m’c without dipole-dipole IMFs
while
LONDON DISPERSION FORCES
of IMFs increase
Attraction of m’c to other m’c due to gravity and instantaneous or temporary dipoles (very weak)
All m’c have them
Higher molar mass, higher boiling point
Strength