Download Lewis Structures and Molecular Models - Corwith-Wesley

KEY
NAME
SECTION
REPORTFOR EXPERIMENT 17
DATE
INSTRUCTOR
Lewis Structures and Molecular Models
For each of the following molecules or polyatomic ions, fill out columns A through G using the instructions provided in the
procedure section. These instructions are summarized briefly below.
A.
B.
C.
D.
E.
'""'"
*""
F.
-:)
G.
Calculate the total number of valence electrons in each formula.
Draw a Lewis structure for the molecule or ion which satisfies the rules provided in the procedure.
Build a model of the molecule and have it checked by the instructor.
Use your model to determine the molecular geometry for this molecule (don't try to guess the geometry without the
model>:tetrahedral, trigonal pyramidal, trigonal planar, bent, linear
Determine the bond angle between the central atom and the atoms bonded to it. If there are only two atoms write "no
central atom" in the space provided.
Use the electronegativity table to determine the electronegativity of the bonded atoms.
.
If the bonds are polar, indicate this with a modified arrow (-)
pointing to the more electronegative element.
If the bonds are nonpolar, indicate this with a short line ( - ).
If there are two or more different atoms bonded to the central atom, include each bond.
Use your model and your knowledge of the bond polarity to determine if the molecule as a whole is nonpolar or a dipole.
Ifit is polar, write dipole in G. !fit is not, write nonpolar.
A
Molecule or
Polyatomic Ion
No. of
Valence
EI ectrons
B
Lewis Structure
C
D
E
F
G
Molecular
Geometry
Bond Angles
Bond Polarity
Molecular Dipole
or Nonpolar
tetrahedral
109.50
C+-+H
nonpolar
1800
C-S
nonpolar
H
4 + 4(1)
I
CH4
8
H-C-H
I
H
4 + 2(6)
CS2
16
:S=C=S:
linear
Molecule or
Polyatomic Ion
C
B
A
No. of
Valence
Electrons
D
Molecular
Geometry
Lewis Structure
E
Bond Angles
F
Bond Polarity
G
Molecular Dipole
or Nonpolar
.
=:c
t:.2j
"'C
0
=:c
1-3
~
0
2(1) + 6
H28
=:c
S
H/""H
8
bent
about 1050
H+--+S
dipole
t:.2j
~
~
=:c
2(5)
N2
:N==N:
10
linear
no central
atom
N-N
nonpolar
2:0:
..
I .,
:O-S-O:
6 + 6(4) + 2
8042~
~
00
I
3(1) + 6 - 1
H3O+
4 + 3(1) + 7
CH3CI
32
..
tetrahedral
I ..
109.50
S +--+0
nonpolar
J
[ H-tH
trigonal
pyramidal
about 1070
H+--+O
::I
....
dipole
~
H
~
I
H-C-CI:
I
14
~
...:t
',,"",
~
0
~.
::I
=
~
~
--
:0:
8
~
~
tetrahedral
109.50
C +--+CI
H+--+C
tetrahedral
109.50
H+--+C
dipole
H
2(4) + 6(1)
C2H6
H
14
H
2(4) + 4(1)
C2H4
H
I I
H-C-C-H
I I
--~
::-:
m
-<
H
H"
/H
/C=C"
H
H
12
nonpolar
trigonal
planar
1200
H+--+C
nonpolar
A
B
D
C
E
G
F
-
No. of
Molecule
or
Polyatomic
Ion
Molecular
I
Electrons
Valence
Lewis Structure
*
2(4)
+C2H2Cl2
2(1) + 2(7)
..
:CI:
24
I
I
H
"
C=C
/
/
Molecular
Dipole
0
or Nonpolar
Bond Polarity
Bond Angles
Geometry
tfj
"tj
H
1200
trigonal
planar
"..
CI:
0
HC
CCI
nonpolar
(as drawn)
tfj
tfj
6 + 3(6) + 2
I-f
26
8032-
I
..
I
I ..
[,o-sol
4 + 2(1)
H
+ 6
CH20
12
I
I
H
about
trigonal
pyramidal
:0:
SO
1070
dipole
t-I
"
/
"'""
C=O
1200
trigonal
..
CO
dipole
=
t!"I-
....
=
f-'
*'"
6 + 2(7)
I
0
HC
planar
OF2
:F../°"..
.' .. '.F:
20
5+ 2(6) + 1
N02-
18
I
I
I
I
:Q:.9
[/N
-J
bent
OF
about 1050
dipole
I;
I
.\
I
bent
I
I
linear
I
about 1190
I
NO
I
dipole
I
2(6)
O2
I
12
:0=0:
I
I
atom
"
**
5 + 3(6)
N03-
+ 1
I
24
:O-N=O:
..
I
I
:0:
U
,
trigonal
I
0-0
no central
1200
planar
*More than one possible Lewis structure can be drawn. See questions 1,2.
**More than one possible Lewis structure can be drawn. See question 3.
nonpolar
I
I
II
,
,
I
I
NO
I
nonpolar
I
".,-,---
REPORT FOR EXPERIMENT
17 (continued)
I
KEY
NAME
QUESTIONS
1. There are three acceptable Lewis structures for C2H2Cl2(*) and you have drawn one of
them on the report form. Draw the other two structures and indicate whether each one is
nonpolar or a dipole.
(a)
(b)
H"
/H
C=C
../
"..
:CI
CI:
..
..
/..CI:
/C=C"..
H
CI:
dipole
:CI:
(c)
H"
H
,,/
/C=C"..
H
CI:
dipole
nonpolar
2. Explain why one ofthe three structures for C2H2Cl2is nonpolar and the other two are molecular dipoles.
The polar C ~ CI bonds cancel each other in 1(c) because the structure is symmetrical.
For 1(a) and 1(b) the C <-+CI bonds do not cancel so the molecules
metrical charge distribution.
do not have a sym-
3. There are three Lewis structures for [N03]- (**). Draw the two structures which are not
on the report form. Compare the molecular polarity of the three structures.
O=N-O: .. I ..
[
:0:
]
:O-N=O .. I ..
[
:0:
]
-
:O-N-O:
..
[
II ..
:0:
]
,
Theyare all nonpolar because the N <-+0 bonds cancel each other in these trigonal planar ions. (One oCthe structures
above.)
will be on the previous
- 150 -
page, the remaning
two will be
i