University of Southern California
MASC 110L
Midterm I
E. Goo
September 26, 2008
Answer all questions. All questions are of equal value. Must show your work
neatly to get full credit.
1. Give the electronic configuration for the following atoms or ions:
a) Si
1s
2
2s
2
2p
6
3s
2
3p
2
Or [Ne] 3s
2
3p
2
b) O
1s
2
2s
2
2p
4
Or [He] 2s
2
2p
4
c) Na
+
1s
2
2s
2
2p
6
Or [Ne]
d) Cl

1s
2
2s
2
2p
6
3s
2
3p
6
Or [Ar]
e) Ti
1s
2
2s
2
2p
6
3s
2
3p
6
4s
2
3d
2
1s
2
2s
2
2p
6
3s
2
3p
6
3d
2
4s
2
is okay
Or [Ar]4s
2
3d
2
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2. Give the steric number of the center atom and predict the shape of the
following molecules
a) CH
4
SN = 4
tetrahedral
b) XeF
2
SN = 5
linear
c) PCl
3
SN = 4
trigonal pyramidal , trigonal pyramid okay
d) XeF
4
SN = 6
square, square planar okay
e) PCl
5
SN = 5 trigonal bipyramidal, trigonal bipyramid okay