Name:
Date:
Period:
EXPERIMENT #19- Molecular Shapes and Structures
Pre-Laboratory Questions:
1.
.
Give a short summary of the two main points of the VSEPR Theory
ing molecules, including the
Draw Lewis Dot Diagrams and predict the bond angles in the follow
AXE notation, name of molecule shape
AXE
Lewis Dot Diagram
Molecule Bond Angle
2.
—
3
PF
6
SF
‘C’s
HBr
e
H
S
2
Name
Section
Lab Instructor
Date_
EXPERIMENT
19
Molecular Shapes and Structures
RESULTSIOBSERVAT)ONS
)
br. c
Sketch (showing bond angles)
(a)
)(D
9I9
(c)CF
(d)
(e)
5
pci
Copyright © Houghton Muffin Co. All rights reserved.
Lewis dotformula
I
Wiccicd
P4rcLnmtd
Experiment 19
232
Report
Sketch (showing bond angles)
Lewis dot formula
iE
(g)
(h)
(oc)
(k)
(I)
(in)
Copyright © Houghton Muffin Co. All rights reserved.
r
j
Lflc
,
1.
234
2.
g and
account the fact that bondin
and sketched do not take into
lt
bui
e
on by
hav
ulsi
rep
you
nt;
dels
exte
mo
e
The
exactly the sam
s do not repel each other to
tron
elec
pe of
of
sha
s
ric
pair
met
g
geo
din
true
bon
non
l this affect the
than by bonding pairs. How wil
r
nge
this
stro
is
by
d
s
nge
pair
cha
g
be
din
d
bon
sure
non
have mea
wn? How will the bond angles you
dra
e
hav
you
les
lecu
mo
the
effect? Use specific examples.
Experiment 19
Report
ble or triple bonds
do not consider those molecules having dou
The models you have built also
of electrons shared
ctures. What effect might a second ot third pair
predicted for their Lewis dot stru
e on the overall shape of a molecule?
between two individual atoms hav
Part II: Build the following models and complete the table
*The UNDERLINED ATOM is the central atom
[MoIecT
*j
Lewis Structure
IAXaEb
Geomethc Shape/Molecular Shape
Draw:
[
3
SO
Name:
Draw:
O
H
C
2
Name:
Draw:
0
F
5
2
3
SO
2
4
SO
3
P0
Name:
Draw:
Name:
Draw:
Name:
Draw:
Name:
Draw:
Name:
POSTLABORATORY EXERCISES:
In actual models, the observed geometries are found sometimes to deviate slightly from the ideal
shapes predicted by the simple VSEPR model described above. Such deviations, can be explained by
considering the different sizes(domains) of bond pairs and lone pairs, or single bonds, double bonds, and
triple bonds, and the effect of changing ligand electronegativity on a bond pair domain. This leads to a
set of basic rules:
The lone pairs on the central atom A and the bonds to A adopt the arrangement that maximizes
their distance apart.
B. Because it is attracted by only one nucleus, a lone pair occupies a larger domain than a bond
pair which is attracted by two nuclei.
of
C. The three electron pairs of a triple bond occupy a larger domain than the two electrons pairs
a double bond, which in turn occupy a larger domain than the single electron pair of a single
A.
bond.
D. The space occupied by a bonding pair domain decreases with increasing electronegativity of the
attached ligand, X, and increases with increasing electronegativity of A, the central atom.
After reading this information answer the following analysis questions.
On the basis of the models constructed in this experiment, what are the Dredicted bond angles
?
4
, and CH
3
0, NH
2
(if you don’t count the lone pairs) in each of H
,
4
, and CH
3
O, NH
2
2. Account for the observed bond angles of 104.5°, 107.3°, and 109.5°, in H
respectively.
O is 93°, and OSO is 123°. Explain why?
5SF
F
F
3. In the molecule 2
.
4
4. Which of the following species does not have a tetrahedral shape? SiCl,,NF,” and SF
1.