Speed of light: c = 2.998 × 108 m/sDepartment of Chemistry, Geosciences, and Environmental Science
Chemistry 1054-010 College Chemistry Fall 2006
Exam 3-A-Key
Name:_______________________________________________________
(Please write your name legibly)
Read all directions and questions carefully!! This exam consists of two parts. The first part consists of 10 multiple choice questions worth four points each for a total of 40 points. The second part consists of five numerical problems worth either 10 or 15 points per question for a total of 60 points. Show all your work necessary for the numerical problems as partial credit will be given for those problems.
Possibly Useful Constants
For light: Speed of light: c = 2.998 × 108 m/s
Planck's Law: 
Planck's constant: h = 6.626 × 10-34 J·s
DeBroglie's wavelength: 
Bohr's model of hydrogen atom: 
Score
Part 1 (40 points):_____________________
Part 2 (60 points):_____________________
Total (100 points):_____________________
Don’t forget to put your name on this test!
Good Luck!!
Part 1
Multiple Choice
Please indicate the answer to each question by putting your choice in the space provided. There is only one correct answer for each question. There will be 10 multiple choice questions worth 4 points each.
1. There are _______ orbitals in the n = 3 shell.
(a) 25 (c) 4
(b) 9 (d) 16
(e) 1
Answer: B
The number of orbitals in a given n shell is equal to n2,
2. The _______________ quantum number determines the shape of the orbital.
(a) principal (n) (c) magnetic (ml)
(b) spin (ms) (d) azimuthal (l)
Answer: D
3. The _________________ have the most negative electron affinities.
(a) alkali earth metals (c) alkali metals
(b) halogens (d) chalcogens
Answer: B
The most negative electron affinities lie on the right hand side of the periodic table.______
4. In which set of elements would all members be expected to have very similar chemical properties?
(a) O, S, Se (c) Na, Mg, K
(b) N, O, F (d) S, Se, Si
(e) Ne, Na, Mg
Answer: A
Elements in the same column have very similar chemical properties.
5. Which ion has the largest ionic radius?
(a) Na+ (c) F¯
(b) O2- (d) Mg2+
(e) Al3+
Answer: B
These are an isoelectronic series of ions. The largest will be the ion with the largest negative charge.
6. Which ion below has a noble gas electron configuration?
(a) Li2+ (c) B2+
(b) Be3+ (d) K¯
(e) Cl¯
Answer: E
7. Which one of the following salts should have the largest lattice energy?
(a) LiF (c) LiBr
(b) LiCl (d) LiI
(e) All of these salts have the same lattice energy.
Answer: A
All of these salts have the same cation (Li+) but different anions (F¯, Cl¯, Br¯, and I¯). The salt with the smallest anion will have the largest lattice energy.
8. Of the atoms below, which is the most electronegative?
(a) Rb (c) F
(b) Cl (d) Si
(e) Ca
Answer: C
9. The most correct Lewis structure for the thiocyanate ion, OCN¯, is shown above. What is the formal charge on the oxygen atom in this Lewis structure?
(a) –2 (c) 0
(b) –1 (d) +1
(e) +2
Answer: B
The formal charge on the oxygen is equal to 6 – 7 = –1.
10. What is the frequency of light (in s-1) that has a wavelength of 1.23 × 10-6 cm?
(a) 3.69 (c) 4.10 × 10-17
(b) 2.44 × 1016 (d) 9.62 × 1012
(e) 1.40 × 10-13
Answer: B
Since c=l×n: 
Part 2
Numerical Problems
Solve the following problems, keeping track of significant figures where applicable. Please show all the work necessary to obtain your answer in order to receive partial credit for possibly wrong answers. Generally, full credit will not be given for the correct answer without any of the work performed to obtain the answer being shown on the paper. Each question is worth either 10 or 15 points.
11. (10 points) Circle the appropriate atom or ion in the lists below. Base your decision solely on the element’s position in the periodic table for parts (a) through (d):
(a) Largest atomic radius:
P S N O Cl
Atomic radius decreases as you go from left to right and increases as you go down. In this series, the largest atomic radius occurs for P.
(b) Smallest 1st Ionization Energy
Br P S Se As
1st Ionization Energy increases as you move from left to right and decreases as you go down. In this series, the smallest 1st ionization energy occurs for As.
(c) Smallest amount of metallic character
Mg Na Si P S
Metallic character decreases as you move from left to right and increases as you go down. In this series, the smallest amount of metallic character occurs for S.
(d) Smallest value of electronegativity
S P As Se Ge
Electronegativity increases as you move from left to right and decreases as you go down. In this series, the most electronegative element is S.
(e) Smallest ionic radius
Ca2+ K+ Cl¯ S2-
For an isoelectronic series of ions ,the smallest has the largest positive charge. This is Ca2+.
12. (15 points) Write the ground state electron configurations for the following atoms or ions. You may use the condensed notation if you wish.
(a) As
33 electrons: 1s22s22p63s23p64s23d104p3 or [Ar]4s23d104p3
(b) Co
27 electrons 1s22s22p63s23p64s23d7 or [Ar]4s23d7
(c) Mn2+
Start with Mn (25 electrons) 1s22s22p63s23p64s23d5
Remove 2e¯ to form Mn2+. They are removed from the 4s subshell first:
___ 1s22s22p63s23p63d5 or [Ar]3d5
(d) P3-
Start with P (15 electrons) 1s22s22p63s23p3
Add 3e¯’s to form P3-: 1s22s22p63s23p6 or [Ne]3s23p6
(e) Cu
29 electrons: 1s22s22p63s23p64s13d10 or [Ar]4s13d10
13. (10 points) Calculate the wavelength of the photon emitted when an electron falls from the n = 4 to the n = 2 level in the hydrogen atom.
Calculate DE: 
Take the absolute value and use Planck’s Law to calculate the wavelength:
14. (10 points) Predict the products of the following reactions and balance the reaction:
(a) K(s) + H2O(l) ¾¾® ??
2 K(s) + 2 H2O(l) ¾¾® 2 KOH(aq) + H2(g)
(b) Na(s) + O2(g) ¾¾® ??
2 Na(s) + O2(g) ¾¾® Na2O2(s)
(c) Ca(s) + F2(g) ¾¾® ??
Ca(s) + F2(g) ¾¾® CaF2(s)
(d) Ba(s) + S8(s) ¾¾® ??
8 Ba(s) + S8(s) ¾¾® 8 BaS(s)
15. (15 points) Draw the most correct Lewis structure for the following molecules or ions:
(a) CHCl3 (c) HNO2
(b) BCl3 (d) SO42-
(e) SiH4 
(10 points extra credit) Give the complete definition for 2 out of the 3 terms below. 5 points will be given for each correct complete definition. Clearly note which 2 definitions you want graded, if you write three definitions without a clear notation, only the first two will be graded.
Electronegativity: the tendency for an atom to attract shared pairs of electrons to itself.
Ionization energy: the energy required to remove an electron from a gaseous atom or ion.
Orbital: the shape of the region in which the electron is likely to be found.