MOLECULAR
SHAPES
 Molecules with 2 electron pair groups around
Linear molecules have polar bonds, but are
the central atom form a linear shape.
usually non-polar.
Bond angle
is 180
Shape is
linear
2 electron pairs
around the
central atom
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MOLECULAR
SHAPES
 Molecules with 3 electron pair groups around
Trigonal planar molecules have polar bonds,
the central atom form a trigonal planar shape.
but are usually non-polar.
Bond angle
is 120
3 electron
pairs
around the
central atom
Shape is
trigonal planar
2
MOLECULAR
SHAPES
 Molecules with 2 bonding pairs and 1 nonbonding
pairhave
groups
around
the
central
atom
Bent
molecules
polar
bonds,
and
are polar.
form a bent shape.
1 Nonbonding pair
Shape is bent
2 bonding pairs
around Bond
the angle
is 120
central atom
3
MOLECULAR
SHAPES

Molecules
with 4 electron
pairsbonds,
groupsand
around
Tetrahedral
molecules
have polar
are
the central
atom form a tetrahedral shape.
usually
non-polar.
4 bonding pairs
around the
Shape is
central atom
tetrahedral
Bond angle
is 109.5
4
MOLECULAR
SHAPES
 Molecules with 3 bonding pairs and 1 nonPyramidal
molecules
havearound
polar bonds,
and are
polar.
bonding
pair groups
the central
atom
form a pyramidal shape.
Shape is
pyramidal
1 Nonbonding pair
3 bonding pairs
Bond angle
around
the
is 109.5
central
atom
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MOLECULAR
SHAPES
 Molecules with 2 bonding pairs and 2 nonBent
molecules
polar
bonds,
are polar.
bonding
pairhave
groups
around
theand
central
atom
form a bent shape.
Shape is
bent
2 Nonbonding pair
2 bonding pairs
Bond angle is
around the
109.5
central atom
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SUMMARY OF
MOLECULAR SHAPES
Linear
Trigonal planar
Bent
Pyramidal
Tetrahedral
Symmetrical shapes
Polar bonds
Non-polar
molecules
Unsymmetrical
shapes
Polar bonds
Polar molecules
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ATTRACTIVE FORCES
IN MOLECULES
 Many differences in the properties of solids and
liquids are associated with the attractive forces
that keep their molecules together.
 These forces range from very strong to very
weak and are responsible for the wide range of
properties observed in these substances.
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ATTRACTIVE FORCES
IN MOLECULES
 Ionic solids have high melting points that are due to
the strong nature of the ionic bond and the forces of
attraction between the cation and the anion.
Na+
ionic bond
Cl
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ATTRACTIVE FORCES
IN MOLECULES
 Covalent molecules also contain attractive
forces, but of a weaker nature than the ionic
compounds.
 The forces between covalent molecules can be
divided into three types:
Dispersion forces
Dipole-dipole
attractions
Hydrogen bonds
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DISPERSION
FORCES
 These forces exist between non-polar
molecules, and are the weakest of the 3 types of
covalent forces.
 These forces are caused by temporary shifts in
distribution of electrons in a non-polar
molecule that cause a temporary dipole.
Temporary dipole
+

FF
+ 
FF
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DIPOLE-DIPOLE
ATTRACTIONS
 These forces exist in polar molecules and are
moderate strength.
 The negative end of a polar molecule is
attracted to the positive end of another such
molecule by these forces.
+

Br
Cl
+

Br 
Cl
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HYDROGEN
BONDS
 These are the strongest of the 3 types of forces
and are formed between molecules that have a
hydrogen attached to the very electronegative
elements (F, O and N).
+

H F
+

HF
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HYDROGEN BONDING
IN WATER
14
15
THE END
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