The Atom
Name: ______________________________
Date: _________________ Period: ________
Honors Chemistry
Atomic Theory
1. Complete the following table by using the following information (create ratios):
Thompson’s charge to mass ratio = −1.76 x 108 C/g
Millikan’s charge of an electron
= −1.6 x 10−19 C/e−
Millikan’s calculated mass of an electron = 9.1 x 10−28g/e−
Number of electrons
5.0 x 1011
3.03 x 10-6
c.
-7.04 x 109
d.
e.
1.00
f.
1
g.
4.6 x 1010
h.
Charge of electrons ( C )
5.0 x 10-5
a.
b.
Mass of electrons (g)
- 1.0
2
Isotopes of Atoms
2. Distinguish between:
a. atomic number and mass number
b. average atomic mass and mass number
3. An isotope is found to have 7 protons and 7 neutrons. What is its
a. atomic number
b. mass number
c. isotopic symbol
4. Circle the symbols that are isotopes of one another.
a.
24
12
X
b.
12
6
X
c.
52
24
X
d.
6
3
X
e.
24
11
X
f.
23
11
X
5. Write the isotope name (hyphen notation) for each element represented in question 4.
a. ________________________
b. _________________________
c. _________________________
d. __________________________
e. __________________________
f. ___________________________
6. Write the isotopic symbols for atoms with the following:
a. 9 p+ and 10 no ________________ b. 25 p+ and 30 no________________
c. 31 p+ and 39 no ________________ d. 1 p+ and 0 no __________________
7. A certain isotope of cobalt is five times as heavy as carbon-12. Write the name and symbol for this
isotope.
____________________________ ________________
8. In each of the following, information on two elements is provided. Given that information, indicate if
the two elements are isotopes of one another by circling the letter (a, b, …).
a. One element contains 22 protons and 24 neutrons while the other has 22 protons and 25 neutrons.
__________________
b. One element has 29 protons and 34 neutrons while the other has 30 protons and 34 neutrons.
__________________
c. One element has 24 protons and a mass number of 50 while the other element has an atomic
number of 24 and has 28 neutrons.
__________________
d. One element is neutral and has 78 electrons and 117 neutrons while the other neutral element
contains 79 electrons and 117 neutrons.
__________________
3
9. Complete the following chart:
Isotopic
Symbol
a. a 16O
8
b. b
Isotope Name
Atomic
Number
Mass
Number
#
protons
#
electrons
#
neutrons
manganese-56
c. c 40
20Ca
d. d
oxygen-18
e. e 19
9F
f. f
rubidium-87
g. g123
51Sb
h. h
nitrogen-15
i. i 210
83Bi
j. j
27
k. k
32
15
l. l
32
7
72
m. m
13
n. n
19
o. o
51
Atomic Mass
10. Determine the average atomic mass of the following mixtures of isotopes.
a. 80.0% I-127, 17.0% I-126, 3.00% I-128
b. 50.0%
197
79 Au ,
50.0%
198
79 Au
13
20
23
4
c. 15.0% Fe-55, 85.0% Fe-56
d. Hydrogen isotopes: (H-1) 99.985% 1.007825 amu, (H-2) 0.0150% 2.014000 amu
e. 95.0%
14
7N,
3.0%
15
7N,
f. 98.0%
12
6C ,
2.0%
14
6C
2.0%
16
7N
g. Uranium has 3 isotopes with the following relative abundances: Uranium-234 (0.0058%), U-235
(0.71%), and U-238 (99.23%). Calculate the average atomic mass of uranium:
Ions
11. An atom that loses electrons has a net __________ charge and is called a(n) _________________.
12. An atom that gains electrons has a net __________ charge and is called a(n) _________________.
13. When a sulfur-32 atom becomes an ion, it typically does so by gaining 2 electrons. What is the
isotopic symbol?
__________________
14. How many protons does Na+ have? ________ electrons? ________
15. How many electrons does P−3 have? ________ protons? _________
5
16. How many electrons does an ion have with an atomic number of 34 and a charge of −2? ________
17. Complete the following chart:
isotopic
symbol
a.
b.
atomic
number
mass
number
8
15
charge
−2
24
d.
25
e.
26
g.
electrons neutrons
63
+
29Cu
c.
f.
protons
13
22
27
10
13
10
32
40
83
80
Moles
18. How many moles of platinum are equivalent to 1.20 x 1024 atoms?
19. Calculate the mass in grams of 9.00 mol of potassium.
20. How many atoms are present in 8.00 mol of chlorine atoms?
21. How many atoms are present in 80.0 mol of zirconium?
126
+4
cation or
anion?
6
22. Find the mass of 1625000 atoms of gold.
23. Determine the number of moles in 100. g of copper.
24. Calculate the number of atoms in 10.0 g of aluminum.
25. Determine the number of moles of helium in 10.0 g of helium.
26. Determine the mass in grams of 10.0 mol of bromine.
27. Determine the mass in grams of 5.00 x 1023 mol of oxygen atoms.
28. How many moles of iron are equivalent to 1.11x1025 atoms?
7
29. How many neutrons are in 3.26 mol of carbon-14 atoms?
30. How many electrons are in 0.653 mol of sodium ions?
31. How many protons are in 37 mg of tungsten atoms?
32. How many joules of heat are required to increase the temperature of 2.01 x 1023 atoms of tin from
13.5°C to 19.3°C?
33. How many moles of helium atoms must be present in a sample for the temperature to increase 11.3°C
when 142.3 cal of thermal energy are added?
34. How many kJ of heat are required to melt a sample of gold containing 1.05 x 1023 atoms?
8
35. How many calories of heat are required to vaporize a sample of molten aluminum that contains
6.04x1022 Al atoms?
36. Krypton has a density of 3.74 g/L at STP. A flask contains 5.58 x 10−3 moles of Krypton atoms at
STP. What would the volume of the flask have to be to hold this sample at a pressure of 700. mmHg
and a temperature of 50.0°C?
37. The density of neon at STP is 0.902 g/L. A balloon contains 5.378 x 1022 Ne atoms at STP. What
would be the volume of the balloon if the pressure was doubled and the temperature was cut in half?
Nuclear Equations
38. Fill in the blank with the isotopic symbol that will complete and balance the following nuclear
equations:
 11 H  ______
a. 21 H  21 H 
Cu 
b.
63
29
c.
241
95
64
30
f.
235
92
Zn


H


Am
d. ______
e.
1
1

U 

2
1
0
1
1
0
e
n
237
93
H
1
0

n
25
13
Al  _______
Np  _______






3
2
He

1
0
n
_______
138
56
Ba
 301 n
 _______
9
39. Write balanced nuclear equations for the following:
a. The alpha decay of neptunium-237
b. The beta decay of bismuth-210
c. The neutron bombardment of tin-120
d. The electron capture of iodine-128
e. The nuclear transmutation of mercury-201 that consists of two alpha decays and 1 beta decay.
f. The electron capture of antimony-123 followed by the emission of 2 neutrons.
g. Alpha-particle bombardment of plutonium-239 produces a neutron and another isotope. Write the
nuclear equation for this reaction and identify the isotope.
h. When bombarded with a neutron, lithium-6 produces an alpha particle and an isotope of hydrogen.
Write the nuclear equation for this reaction. What isotope of hydrogen is produced?
i. With what particle would you bombard sulfur-32 with to produce hydrogen-1 and phosphorus-32?
Write the appropriate nuclear equation.
j. With what particle would you bombard bismuth-209 to produce astatine-211 and 2 neutrons?
Express this reaction in the form of a nuclear equation.
10
Half Life
40. A radioactive isotope of radon has a half life of 3.8 days. How long will it be before only 1/16 of the
original sample of radon remains?
41. A 1.000-kg block of phosphorus-32, which has a half-life of 14.3 days, is stored for 100.1 days. At
the end of this period, how much phosphorus-32 remains?
42. How much time will be required for a sample of radioactive tritium (t1/2 = 12.5 years) to lose 75 % of
its radioactivity?
43. A sample of air from a basement is collected to test for the presence of radon-222, which has a halflife of 3.8 days. However, delays prevent the sample from being tested until 7.6 days have passed.
Measurements indicate the presence of 6.5 g of radon-222. How much radon-222 was present in the
sample when it was initially collected?
44. The half-life of carbon-14 is 5720 years. An artifact is found to contain 0.21 g of carbon-14. Based
on the quantity of carbon-12 present, it was determined that the sample, if new, would contain 3.36g
of carbon-14. How old is the sample?
45. A piece of wood is known to be 34,200 years old. At the present time, the wood contains 4.0 g of
carbon-14. How much carbon-14 was in the wood originally?
11
46. Gold-191 has a half-life of 12.4 hours. After one day and 13.2 hours, 10.6 g of gold-191 remains in a
sample. How much gold-191 was originally present in the sample?
47. There are 3.29 g of iodine remaining in a sample originally containing 26.3 g of iodine-126. The halflife of iodine-126 is 13 days. How old is the sample?
48. A meteorite strikes the earth in western Wyoming. Chemical analysis shows that it contains 44.62 kg
of radioactive iron-59 (t1/2 = 44.3 days). Approximately, how much of this isotope will remain in the
meteorite after 220 days?
49. A sample of pure radium-226 (t1/2 = 1620 yrs) is donated to a museum in the year 1990. The sample
weighs 5.0 mg. The museum decides to replace the sample after it has been reduced in weight to 0.62
mg. In what year will the sample have to be replaced?
Review
50. Complete the table for the atoms indicated:
Isotopic
Atomic
Isotope Name
Symbol
Number
23
11
Mass
Number
# of e-
#of p+
# of n0
Na
8
19
Mercury-201
10
10
12
51. Complete the table below:
Ion A
Ion C
13
a. What is the atomic number?
b. What is the mass number?
Ion B
33
c. How many protons?
d. How many electrons?
18
36
e. How many neutrons?
15
42
f. What is the charge?
+3
-3
g. Write the isotopic symbol
h. What kind of ion?
i. Change in # of electrons
Gain 2
52. A sample of neon gas is composed of 90.92 % neon-20, 0.257 % neon-21 and 8.82 % neon-22.
Calculate the atomic mass of neon. (show work)
53. How many atoms are in 2.89 moles of krypton?
54. How many grams of barium are in 0.548 moles of barium atoms?
55. How many moles of silicon are in 125.6 g Si?
13
22
56. How many grams of lithium are in a sample containing 2.3 x 10 Li atoms?
57. Write the nuclear equation for the:
a. beta decay of radium-226
b. alpha decay of protactinium-231
c. The electron capture of Uranium – 238
d. The transmutation of curium-247 beginning with a neutron bombardment followed by an
alpha decay.
58. What three conclusions were drawn from Rutherford’s experiment?
59. Cite 3 examples of the concepts learned in this chapter that can be used to dispute Dalton’s
Atomic Theory.
60. What device was Thomson using that led to the discovery of electrons?
14
Multiple Choice Questions
Directions: Circle the response the best completes the statement.
1. Dalton’s atomic theory did NOT include the postulate that
a. matter is made of small particles called atoms.
b. atoms contain electrons, protons, and neutrons.
c. atoms are neither created nor destroyed in chemical reactions.
d. compounds always contain the same relative numbers and kinds of atoms.
2. J.J. Thomson concluded that the cathode ray contains negatively charged particles by studying how
a. the cathode ray produced a green spot on the fluorescent screen.
b. a magnetic field deflected the ray’s path.
c. the ray was deflected by electrically charged plates.
d. both b and c
3. Rutherford’s Alpha Scattering Experiment indicated that
a. the nucleus of an atom occupies most of the atom’s volume.
b. positive charges are dispersed throughout the atom.
c. positive charges are concentrated in a very small core at the atom’s center.
d. protons and neutrons are located in the nucleus.
4. An atom is
a. a tiny, indivisible particle.
b. the smallest piece of matter.
c. the smallest particle of an element that retains the chemical identity of that element.
d. an artificially assembled unit that contains protons and electrons.
5. Atoms of each element contain a unique number of
a. neutrons in their nuclei.
b. protons in their nuclei.
c. electrons in their nuclei.
d. all of the above
6. Two isotopes of the same element may have different
a. mass numbers and atomic numbers.
b. numbers of protons and numbers of neutrons.
c. mass numbers and numbers of neutrons.
d. chemical properties.
15
61. An isotope of mass 42g is allowed to decay over time. After 27.4 days, the isotope had a mass of 5.25
g. What is the half life of this isotope?
62. What mass would the isotope described in the previous question have if it was allowed to sit for a
total of 11 half lives?
63. How many electrons would it take to have a combined mass of 1.77×10−5 g?
64. What is the mass and charge of 1.95 moles of electrons?
Cumulative Review
65. Determine the number of significant figures in each of the following:
a)
6.7090
b) 0.0384
c) 12,000
66. Three segments of a line are measured to be 12.5 mm, 1.1 in and 2.365 cm. What is the length of
the line?
67. Identify each of the following as a physical (P) or Chemical (C) change.
____ a) sodium chloride is dissolved in water
____ b) gasoline is burned in an automobile engine
____ c) water boils
16
____ d) when sodium iodide and lead sulfate are mixed, a yellow precipitate forms
68. Identify each of the following as an element (E), compound (C), Homogeneous mixture (Hom) of
Heterogeneous mixture (Het).
____ a) salt and water
____ d) sand and water
____ b) hydrogen
____ e) water
____ c) sodium chloride
____ f) uranium
69. A 16.3 gram sample of sulfur dioxide gas occupies 56.2 mL at a pressure of 772 mm and a
temperature of 95.6°C. What is the volume of the gas at STP?
70. A student measures the mass of an object as 135.80 g. Calculate the percent error in the
measurement, given that the accepted value for the mass is 137.23 g.
71. Convert 4.5 millimeters to kilometers. Express your answer in scientific notation.
72. Lead has a density of 11.4 g/cm3. How many atoms of lead are in 0.567 ft3 block of lead?
73. A 157 mg sample of helium at 22.5˚C absorbs 13.9 cal of heat energy. What will the temperature
of the helium be after it absorbs the energy?