CHEM 107 (Spring-2007)
Exam 3 (104 pts)
Name: ------------------------------------------------------------------------, Clid # -----------------------------LAST NAME, First
(Circle the alphabet segment of your LAST NAME): A & B
C-G
H-L
M-P
R-Z
Please answer the following questions:
Part I: Multiple Choices (52 pts: 13 @ 4 pts each + 4 pts bonus). Circle the ONE best answer:
1. An Co3+ ion is
a) paramagnetic with four unpaired electrons
b) diamagnetic with zero unpaired electrons
c) paramagnetic with two unpaired electrons
d) paramagnetic with one unpaired electron
2. The orbitals of 2p electrons are often represented as being
a) elliptical
b) tetrahedral
c) dumbbell shaped
d) spherical
3. Which set of quantum numbers is correct and consistent with n = 4?
a) ℓ = 3, mℓ = -3, ms = +½
b) ℓ = 4, mℓ = +2, ms = -½
c) ℓ = 2, mℓ = +3, ms = +½
d) ℓ = 3, mℓ = -3, ms = +1
4. The ground state electron configuration of lead, Pb (Z = 82) is
a) [Xe] 5d10 6s2 6p2
b) [Xe] 4f14 6d10 6s2 6p2
c) [Xe] 4f14 5d10 6s2 6p2
d) [Xe] 6s2 6p2
5. The maximum number of electrons that can occupy an orbital labeled 4px is
a) 6
b) 4
c) 2
d) 3
6. The ground state electron configuration of chromium atom, Cr (Z = 24) is
a) 1s2 2s2 2p6 3s2 3p6 4s2 3d4
b) 1s2 2s2 2p6 3s2 3p6 4s1 3d5
c) 1s2 2s2 2p6 3s2 3p6 3d6
d) 1s2 2s2 2p6 3s2 3p6 4s2 4p4
7. Which of the following has the highest ionization energy?
a) Xe
b) K
c) Cl
d) Ne
8. When the three elements S, Se and Cl are arranged in order of increasing atomic radius, which is
the correct order?
a) Se < S < Cl
b) S < Cl < Se
c) S < Se < Cl
d) Cl < S < Se
9. Which of the following bonds is considered to be the least polar?
a) O-F
b) C-F
c) N-F
d) Si-F
1
10. Which of the following electromagnetic radiation has the shortest wavelength?
a) X-ray
c) γ-rays
b) Visible light
d) Infrared
11. Which of the following isoelectronic species would have the smallest radius?
a) Na+
b) Al3+
c) F-
d) N3-
12. Which compound has a triple bond?
a) O2
b) BrCN
c) BeF2
d) CO2
13. Which of the following molecules is most likely to have bond angle close to 109°?
a) XeF4
b) SF4
c) CF4
d) NF3
14. Which of the following molecules is classified as predominantly ionic?
a) SeO2
b) Cl2O7
d) P4O10
d) SrS
Part III. Bonding (30 pts):
1.
(20 pts) Draw the Lewis structure of the following molecules or ions?
a) SF4
b) CO32-
c) XeF4
a) SF4
b) CO32-
c) XeF4
d) O3
d) O3
2
2. (10 pts) Draw the Lewis structure for the laughing gas dinitrogen oxide, N2O (NNO), draw the
resonance structures, if there is any then: predict:
a) number σ and π bonds
b) The molecular shape of the ion
Lewis Structure & resonance structures (if any)
a) Molecular shape: -----------------------b) # of σ bonds ----------
and
# of π bonds ----------c) # nonbonding e’s on the central atom -----
Part III. Calculations (18 pts) Show all work for full credit. Please express all answers with the
proper units and correct number of significant figures.
1. (12 pts) a) Calculate the wavelength in nanometers in the H-atom spectrum that arises from the
electron transition of n = 5 to n = 2.
λ (nm) =
b) In what spectral region does this transition occur?
--------------------------------------------------
c) Is energy absorbed or emitted?
--------------------------------------------------
2. (6 pts) Calculate the ground state energy, in joules of the electron in the H atom.
3
PREFERENCE SHEET FOR
CHEM 107
Exam 3 –Spring 2007
You will have 55 minutes to complete this exam. The exam has 3 pages plus the Periodic Table and
Reference page. When you are told to do so, tear off the Periodic Table cover sheet and use as required
during the exam.
Equations and Constants:
ν = RH/h [1/(nlo)2 – 1/(nhi)2]
En = -RH/n2
E=hν
c=λν
RH = 2.180 x 10-18 J
h = 6.626 x 1034 J.s
c = 3.00 x 108 m/s
Avogadro’s Number = 6.022 x 1023
1
1
2
H
Periodic Table of the Elements
He
1.01
3
2
3
4
5
6
4.00
4
5
6
7
8
9
10
Li Be
B
C
N
O
F
Ne
6.94
9.01
10.81 12.01 14.01 16.00 19.00 20.18
11
12
13
14
15
16
17
Na Mg
Al Si
P
S
Cl Ar
22.99 24.30
26.98 28.08 30.97 32.06 35.45 39.95
21
19
20
K
Ca Sc Ti V
39.1
40.08 44.96 47.88 50.94 52.00 54.94 55.85 58.93 58.69 63.55 65.38 69.72 72.59 74.92 78.96 79.90 83.80
37
38
39
Rb Sr Y
22
40
23
41
24
25
26
27
28
29
30
31
32
33
34
35
18
36
Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
42
43
44
45
46
47
48
49
50
51
52
53
Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I
54
Xe
85.47 87.62 88.91 91.22 92.91 95.94 (98)
101.1 102.9 106.4 107.9 112.4 114.8 118.7 121.8 127.6 126.9 131.1
55
76
56
57
72
73
74
75
77
Cs Ba La Hf Ta W Re Os Ir
78
79
80
81
82
83
84
85
86
Pt Au Hg Tl Pb Bi Po At Rn
132.9 137.3 138.9 178.5 181.0 183.8 186.2 190.2 192.2 195.1 197.0 200.6 204.4 207.2 209.0 (209) (210) (222)
87
7
88
89
104 105 106 107 108 109 110 111 112
Fr Ra Ac Rf Db Sg Bh Hs Mt Uun Uuu Uub
(223) 226.0 227.0 (261) (262) (263) (262) (265) (266) (269) (272) (277)
58
59
60
61
62
63
64
65
66
67
68
69
70
71
Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
140.1 140.9 144.2 (145) 150.4 152.0 157.2 158.9 162.5 164.9 167.3 168.9 173.0 175.0
90
91
92
Th Pa U
93
94
95
96
97
98
99
100 101 102 103
Np Pu Am Cm Bk Cf Es Fm Md No Lr
232.0 231.0 238.0 237.0 (244) (243) (247) (247) (251) (252) (257) (258) (259) (260)
4