Powerpoint to explain the different types of IMF

2. We have been working on
intramolecular force (forces in bonds).
Intermolecular forces- forces which
hold full molecules together.
-ionic molecules have the
strongest attraction due to their full
positive and negative charges.
-this high electromagnetic
attraction (+ and -) results in ionic
molecules staying more tightly
together than covalent molecules.
= higher melting point for ionics!

3. Covalent intermolecular forces:
(we will go weakest to strongest)
1) Dispersion force-
-Often called London Force after Fritz London.
-weakest of three covalent forces.
-only force that keeps non-
polar molecules together since
they have no true + or -
attraction. But dispersion forces
occur in all molecule types.
-the larger the molecule, the
more dispersion force it will have
(more electrons).

4. 2) Dipole-Dipole Force-
-stronger than dispersion forces.
-occurs in weaker polar molecules
because of their partial positive and
negative charges. (δ+ and δ-)
animation
Draw HCl and show charges.
Hδ +—Clδ -
Hδ +—Clδ -
Hδ +—Clδ -
-dipole-dipole is for all polar molecules except
H-F, H-O or H-N. (they have a stronger force)

5. 3) Hydrogen Forces- strongest IM covalent bond
-”Hydrogen forces are a lot of FON”
(hydrogen with F,O and N only)
-the ΔEN is so great between H
and FON that the whole molecule
has a very strong δ+ and δ- end.
H = 2.1 F = 4.0
ΔEN = 1.9 (is
almost ionic!!!)

6. -these stronger δ+ and
δ- ends create a greater
force than dipole-dipole
which has weaker
partial charges.
Ex. Water
-hydrogen forces are
essential for making the
molecules of life… DNA
and proteins.

7. Weakest
Strongest
Dispersion
(London)
Dipole-
Dipole
Hydrogen
forces
Ionic bonds
(electromagnetic)
Melting point
Lowest
highest