Chemistry Reference
In-Depth Information
Solution
The 8 valence electrons, 6 from oxygen and 2 from hydrogen, are oriented
toward the corners of a tetrahedron. Adding hydrogen atoms to any 2 of those
electron pairs results in a nonlinear molecule. The shape of water is described
as
nonlinear, angular,
or
bent.
Practice Problem 13.8
Determine the shapes of (a)
PCl
3
,
(b)
SF
2
,
and (c) HI.
In summary, the four electron pairs tetahedrally oriented around a central
atom give rise to different
molecular
geometries because of the different num-
bers of atoms that are attached (Figure 13.6).
Compounds with multiple bonds are only slightly different. The electrons
in each multiple bond are considered to be one group of electrons.
The electrons in each multiple
bond are considered to be one
group of electrons.
EXAMPLE 13.9
Determine the shape of the sulfur dioxide molecule.
Solution
The 6 valence electrons of sulfur and the 6 from each oxygen atom make 18
total. The electron dot diagram for
SO
2
is
O
S
O
The double bond is considered one electron group, the single bond is another,
and the lone pair is a third. The three groups arrange themselves as far apart
as possible:
120°.
The addition of the oxygen atoms results in an angular
molecule:
S
O
O
Practice Problem 13.9
Determine the geometry of the
SOF
2
mole-
cule, in which the S atom is the central atom.
H
N
C
O
F
H
H
H
H
H
H
H
Trigonal pyramidal
H
Tetrahedral
H
Nonlinear
Linear
Tetrahedral Orientation of Electron Pairs Leads to Different Molecular Geometries
Figure 13.6
