Warm Up:
Octet Rule
 a filled layer contains 8 electrons
 Exceptions (After bonding…)
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H and He will have 2
Beryllium will have 4
Boron will have 6
Some transition metals can have more than
8
Dot Diagrams for
Molecules
 Atom with most unshared electrons goes in
middle *capable of forming most bonds*
 Count to make sure you have the right number
of electrons
 Each atom wants to have a full valence
 Try these…
 CH4
O2
CO2
 NH3
N2
H2O
Domains
 Write the shapes of each of
the dot diagrams you made
before
Warm Up: Label the following
bonds as polar and nonpolar.
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Br2
HCl
H2
CH4
NH3
Molecular Polarity
Dipole
 Molecule with an overall unequal
distribution of electrons
Two atom molecules
 If the bond is non-polar, so is the
molecule
 If the bond is polar, the molecule has a
dipole and is polar
Do these molecules have
dipoles?
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N2
O2
CO
HF
Three atom molecules
 If the 2 polar effects are equal and
oppositely directed, the molecule is
nonpolar
 Otherwise, the molecule is polar
Carbon dioxide
water
Four atom molecules
 It is possible that the 3 polar effects may
cancel and produce a nonpolar molecule
 It is also possible that they don’t cancel
and produce a polar molecule
Exception to octet rule
NH3 (ammonia)
Five atom molecules
 It is possible that the 4 polar effects may
cancel and produce a nonpolar molecule
 It is also possible that they don’t cancel
and produce a polar molecule
CH4
CH3Cl
Intermolecular Forces
 Between molecules
 Dipole-dipole
 Hydrogen bonding
 Van der Waals
Dipole-Dipole
 Like electrical charges and magnets,
dipoles can attract one another
 Stronger attractions with stronger dipoles
 Stronger attractions when molecules are
closer together with lower temperature and
higher pressure
Hydrogen Bonding
 Occurs when
Hydrogen and
Fluorine, Oxygen, or
Nitrogen are present
 FON
 Ammonia, hydroflouric
acid, water
 Higher boiling points
with hydrogen bonding
Van der waals
 Recall that electrons have a little bit of freedom
to move around their electron clouds
 VDW are produced by momentary uneven
electron distributions
 Extremely weak
 Responsible for bonding of nonpolar
molecules, liquefaction of inert gases, 3
phases of halogens at STP
 Stronger for molecules with more electrons
 Gets stronger as molecules get closer
bromine