Ch221, W’14, Practice Exam #2
1. Give the BEST Lewis structures for:
(a) COBr2
(b) XeF6
(c) CH2CHCN (arrangement = C C C N)
2. Give all of the resonance hybrids for CH2NO2- (note the negative charge), where the
hydrogens are attached to the carbon and the oxygens to the nitrogen.
MO Theory
1. (a) (6 pts) Describe the bonding in the
partial credit.
O 22 by filling in the attached molecular orbital diagram. No
(b) (1 pts) Show bond order calculation.
(c) (1 pt) State any magnetic properties.
3. (10 pts total) Given the Lewis structure for formaldehyde, H2CO
H
\
..
..
C=O
/
H
(a) (6 pts) Give the hybridizations for both carbon and oxygen (we are hybridizing each
atom).
hybridization for carbon = __________ hybridization for oxygen = ____________
(b) (2 pts) On the left is the orbital box diagram for the valence shell of carbon. Determine
the hybridization of the carbon atom according to your answer in part (b), and indicate
what the orbital box diagram for the hybridized carbon atom looks like on the right side of
the “” symbol. Fill in the electrons according to the required bonding.
E

(c) (2 pts) Do the same thing for the oxygen atom.
E

(d) First sketch the -bonding in the molecules, and in a separate sketch, draw the bonding (similar to Figure 5.26 on p. 204 in the book)
Multiple Choice - each question is worth 3 points and there is only one BEST answer.
1. Which of the following elements is most likely to form compounds involving an expanded
octet?
(a) Li
(b) N
(c) F
(d) Ne
(e) S
2. The covalent bond with the greatest polarity would form between which of the atom pairs
below?
(a) Br – Br
(b) S – O
(c) C – P
(d) C – O
(e) B – O
3. Which of the elements listed below is the least electronegative?
(a) Sr
(b) V
(c) Ni
(d) P
(e) I
4. Which one of the following molecules has an atom with an expanded octet?
A. HCl
B. AsCl5
C. ICl
D. NCl3
E. Cl2
5. Which one of the following molecules has an atom with an incomplete octet?
A. NF3
B. H2O
C. AsCl3
D. GeH4
E. BF3
6. Predict the molecular geometry and polarity of the SO2 molecule.
A.
B.
C.
D.
E.
linear, polar
linear, nonpolar
bent, polar
bent, nonpolar
None of the above.
7. According to the VSEPR theory, the F –As –F bond angles in the AsF4– ion are predicted
to be
A.
B.
C.
D.
E.
109.5o
90o and 120o
180o
< 109.5o
< 90o & < 120o
8. According to the VSEPR, theory the geometry of the atoms in the carbonate ion, CO32– is
A.
B.
C.
D.
E.
square planar.
tetrahedral.
pyramidal.
trigonal planar.
octahedral.
MO's for the Homonuclear Diatomics O2 and F2
(the 2p and 2p’s are reversed compared to the rest of the second period)
____
*2px
____ ____
*2py *2pz
___ ___ ___
2p
___ ___ ___
2p
____ ____
2py 2pz
____
2px
____
*2s
___
2s
___
2s
____
2s
____
*1s
___
1s
___
1s
____
1s