CHAPTER 9- Chemical bondings II:
Molecular Geometry and Hybridization of Atomic Orbitals Prof. Onwuachi
1. Using VSEPR model, predict the molecular geometry (molecular shape) and
electron geometry of the followings:
O3 =>MG = bent; EG = trigonal planar
CO32- => MG = trigonal planar;
EG same
ICl2 => MG = linear;
EG = trigonal bipyramidal
NF3 => MG = trigonal pyramidal;
EG = tetrahedral
SnCl3 => MG = trigonal pyramidal;
EG = tetrahedral
2. Predict the approximate value for the bond angles for each carbon
indicated in the
following compounds:
H
H
(a) H - C - C  C -H
(b) H - C - O -H
H
H
109.5º, 180º, 180º
109.5º
3. Predict whether the following molecules are polar or nonpolar;
H
Cl
C=C
Cl
Cl
H
H
C=C
Cl
H
SO2 P
NF3 P
CS2 NP
NP
P
4. Indicate the hybridization of orbitals by the central atom in each of the
following;
SO32- sp3
SO3 sp2
NH4+ sp3
SCl2 sp3
5. Consider the following molecules , answer the following questions for only
marked
(*)carbons.
Cl
H H
*
(a) O = C
(b) H - C* - C* = C - C*  N
Cl
H
H
I) predict the bond angles
II) give hybridizations
120, 109.5, 120, 120, 180
sp2, sp3, sp2, sp2, sp
III) determine the total number of sigma () and pi () electrons in the
molecules. (a) 6  , 2 
(b) 18 , 6 
IV) predict the molecular geometry ( molecular shape) and electron
geometry around each marked carbon.
(a) MG = trigonal planar, EG = same
(b) Carbons 1,2,3,4 respectively: MG = tetrahedral, trigonal planar, trigonal
planar, linear. EG = same
6. Draw Lewis dot structures for following molecules and ions, predict which
will exhibits delocalized pi () bonding ( resonance structure).
SO32- No
NH4+ No
NO2 Yes
NCS- Yes
OCN- Yes
I3- No
7. Consider the following molecules and ions:
He2- σ21s σ*21s σ12s
C22- σ21s σ*21s σ22s σ*22s π22px π22py σ22pz , B.O = 3, stable
O22+ σ21sσ*21sσ22sσ*22sσ22pzπ22pxπ22py , B.O =3, stable
CN- σ21sσ*21sσ22sσ*22sπ22pxπ22pyσ22pz , B.O. =3, stable
N2- σ21sσ*21sσ22sσ*22sπ22pxπ22pyσ22pzπ*12px , B.O. = 2.5, stable
a) write molecular orbital electron configuration
b) predict the bond order
c) predict the stability (stable or unstable)
8. Consider CH3 , CH3+ , and CH3-, for each: You do these.
a) draw Lewis dot structure
b) predict electron geometry and molecular geometry
c) using hybrid orbitals , describe the bonding ( orbital hybridization)
d) predict the bond angles
e) predict the polarity ( polar or non-polar)
For
CH3-
b) CH3+
••
(a )
[ H - C - H ]H
(b) tetrahedral/ trig pyramidal
(c)
sp3
(d) 107.5º
(e)
polar
[ H - C - H ]+
H
trig. Planar/ trig. planar
sp2
120º
nonpolar
9. Consider for each
H2 You do for this chemical specie.
H2+ You do for this chemical specie.
H2- For This specie: (a) σ21sσ*1 , (b) 3 e-, (c) H-H•, (d) B.O. = ½, (e) paramagnetic
(f) (H2+ , H2- ) < H2 . These are responses to queries (a) to (f) below for H2- .
___*1s
1s 
↓  1s
 1s
a) draw energy-level diagram.
b) determine total number of electrons.
c) write Lewis dot structure.
d) calculate the bond order.
e) determine the magnetic properties(in terms of paramagnetic or
diamagnetic).
f) Compare the stability and arrange the in order of increasing stability.
10. Identify the following molecules or ions as stable or unstable. Explain why?
Compare the stability.
He2 unstable, bond order is zero.
He2+ stable, bond order is 0.5
O2 stable, bond order is 2
O2- stable, bond order is 1.5
O22- stable, bond order is 1
Order of increasing stability:
He2 < He2+ < O22- < O2- < O2