SO

: 2
There is a lone pair on the S (an AX

E molecule), so the molecule is bent with a 2

bond angle of ~120

o. The Lewis structure is shown below and the ball-and-stick and

space-filling representations are shown in the margin.

Ball-and-stick and space-filling models of SO

(^2)
OSO=
O SO
O
S
O
~120
o
H^2
O:
There are two lone pairs on the oxygen atom, so H
O is an AX 2
E 2
molecule. The 2
four electron regions adopt the arrangement show
n in Figure 6.1c, which results in a bent
shape and a bond angle of ~109
o (Figure 6.2c and margin). Note that drawing water with
the four regions in the plane of the paper
makes it appear that the two hydrogen atoms
can either be next to one another or opposite
one another. In fact, all four positions are
equivalent, so the structure is the same no matter which two positions are occupied by the hydrogen atoms.
Ball-and-stick and space-filling models of H
O 2
HO
H
HO H
H
O
H~109
o

Example 6.2
Predict the shapes of SO
and CF 3
and estimate their bond angles. 4
SO
: 3
The Lewis structure (Example 5.10) indicates that SO
is an AX 3
molecule. The 3
three electron regions, which are identica
l due to resonance, adopt the arrangement
shown in Figure 6.1b and in the margin. The molecular shape is trigonal planar (Figure 6.3a), and the three identical O-S-O bond angles are 120
o..^
Ball-and-stick and space-filling models of SO
(^3)
O S
OO
OS
O
O
+2
+2
120
o^
CF
: 4
The four shared pairs adopt the arrangement shown in Figur
e 6.1c. All of the regions
are occupied by atoms, so the molecular
geometry is tetrahedral (Figure 6.3c and
margin). The actual bond angles
are the predicted values (109
o) because all of the
regions around the carbon are the same.
F C
FF
F
F
F
C
FF
109
o^
Ball-and-stick and space-filling models of CF
(^4)
Chapter 6 Molecular Structure & Bonding
© by
North
Carolina
State
University