Lewis Symbolism, Molecular Structure (VSEPR),
and Hybridization (VB Theory)
1. Draw the Lewis structures for the following molecules or ions:
NH4+
CH2Cl2
H
H N H
H C N:
H
CO32..
:O :
+
H
..
:
H C Cl
..
: Cl:
..
HCN
C2H4
H
2-
H :O:
H C C H
..
: O C O:
..
..
CH3CO2H
H
..
H C C O
.. H
H
(With the two other
resonance hybrids)
2. Draw the Lewis structure of benzene, C6H6. Benzene is a 6-carbon ring molecule. Show also the
conventionally used abbreviated drawing of benzene.
H
H
H
C
C
C
C
C
C
H
H
H
3. Draw the Lewis structure of parahydroxybenzoic acid, (PABA, C7H6O3). PABA is an excellent
UV-radiation absorber once used in sunscreens. As the name implies, PABA contains the benzene
ring and the carboxylic acid group. The prefix “para” means “across the ring”.
H
H
C C :O:
..
..
H O
C
C
C
O
.. H
..
C C
H
H
1
5. Two kinds of covalent bonds exist; nonpolar covalent and polar covalent. Describe the carbonhydrogen bond in CH4 as either polar or nonpolar.
6. Draw the Lewis structures of the following molecules or ions. For each, indicate the electronic
geometry, molecular geometry, hybridization (if any) of central atoms, and whether the molecule
or ion possesses a permanent dipole moment.
PO43..
:O:
SeO2
3-
..
..
:O Se
:O
.. :
.. P .. :
O
:O
..
..
:O
.. :
This ion may have 1
double bond.
electronic geometry
N2H4
..
..
H N N H
H
H
This ion shows
resonance.
__tetrahedral______
___trigonal planar__
_tetrahedral both N
molecular geometry __tetrahedral______
___bent___________
_trigonal pyramidal
hybridization
___sp3 (on P)______
___sp2 (on Se)_____
_sp3 (both N)_____
Dipole Moment
___no____________
___yes____________
_yes____________
XeF4
CBr4
.. .. ..
: ..
F:
F
.. Xe ..
..
: ..
:
F
F
.. ..
C2H2
Br
Br
C Br
Br
H C C H
Lone-pairs omitted
because I was tired.
electronic geometry
__octahedral_______
__tetrahedral______
__linear (both C)__
molecular geometry __square planar____
__tetrahedral______
__linear (both C)__
hybridization
__sp3d2 (on Xe)____
__sp3 (on C)_______
__sp (on C)_______
Dipole Moment
__no_____________
__no_____________
__no____________
2
NO2..
:O
..
N
SeO42-
O
2-
Se O
O
O
O
.. :
This ion shows
resonance.
electronic geometry
N2F2
..
..
..
..
:..
F N N F
..:
:..
:..
F:
F:
This ion may have 1 or
2 double bonds.
___trigonal planar__
__tetrahedral______
_tetrahedral both N
molecular geometry ___bent___________
__tetrahedral______
_trigonal pyramidal
hybridization
___sp2 (on N)______
__sp3 (on Se)______
_sp3 (both N)_____
Dipole Moment
___yes____________
__no_____________
_yes____________
CF2Cl2
C2H4
_________________
_________________
________________
molecular geometry _________________
_________________
________________
hybridization
_________________
_________________
________________
Dipole Moment
_________________
_________________
________________
SO3
electronic geometry
3
NO
electronic geometry
PBr5
SF6
_________________
_________________
________________
molecular geometry _________________
_________________
________________
hybridization
_________________
_________________
________________
Dipole Moment
_________________
_________________
________________
7. Shown below is the molecule caffeine. Describe the hybridization of every atom that uses
hybridized atomic orbitals for bonding. Determine the approximate bond angles. Also indicate the
type of bonds formed between atoms (i.e., σ(sp2-p), π(p-p), etc.) Notice that lone-pairs are omitted
but assumed present; this convention is typical of many drawings of organic molecules.
O
CH3
H3 C
N
N
O
N
N
CH3
Atom
1
2
3
4
5
6
7
8
9
10
11
12
Hybridization
sp3
sp3
sp2
sp2
sp2
sp3
sp2
sp3
sp2
sp2
sp3
sp3
Bond Angle
on Atom
109.5°
~107°
~120°
~120°
~120°
~107°
~120°
109.5°
~118°
~120°
107°
109.5°
H3C
O
12
O
1
2
3
N
7
CH3
4
10
6
N
5
CH3
8
4
N 11
N
9