Name ____________________________________________
Date ____________________
Class ___________________
4
The Structure of the Atom
Reviewing Vocabulary
Match the definition in Column A with the term in Column B.
Column A
Column B
______ 1. Radiation deflected toward the positively charged plate
a. atom
______ 2. Atoms with the same number of protons but different numbers of neutrons
b. nucleus
______ 3. High-energy radiation that has no charge and no mass
c. atomic mass
______ 4. The smallest particle of an element that retains the properties of that element
______ 5. The weighted average mass of an element’s isotopes
______ 6. The center-most part of an atom where the protons and neutrons are contained
______ 7. Radiation deflected toward the negatively charged plate
d. isotopes
e. gamma ray
f.
alpha radiation
g. beta radiation
______ 8. The rays and particles emitted by radioactive material
h. atomic mass
unit
______ 9. Equal to 1/12 the mass of a carbon-12 atom
i.
radiation
_____ 10. Ray of radiation traveling from the cathode to the anode
j.
Dalton’s atomic
theory
_____ 11. Process (not requiring energy) by which unstable nuclei lose energy
_____ 12. States that all matter is composed of atoms
k. cathode ray
l.
_____ 13. Process whereby some substances spontaneously emit radiation
radioactivity
m. radioactive
decay
Compare and contrast each pair of related terms.
14. mass number, atomic number
______________________________________________________________________________________________
______________________________________________________________________________________________
______________________________________________________________________________________________
15. nuclear reaction, nuclear equation
______________________________________________________________________________________________
______________________________________________________________________________________________
______________________________________________________________________________________________
Chemistry: Matter and Change
1
Chapter Assessment
Name ____________________________________________
Date ____________________
Class ___________________
4
Understanding Main Ideas (Part A)
Use the periodic table to identify each element described below.
1. atomic number 65 __________________
2. 78 protons __________________
3. 44 protons and 44 electrons __________________
4. atomic number 24 __________________
5. 21 protons __________________
6. atomic number 55 __________________
In the space at the left, write true if the statement is true; if the statement is false, change the
italicized term to make it true.
_________________ 7. An atom’s nucleus contains its protons and electrons.
_________________ 8. Neutrons have no electrical charge.
_________________ 9. Beta particles have a charge of 2.
________________ 10. An alpha particle consists of two protons and two electrons.
Complete the table below.
Isotope
Symbolic Notation Number of Protons Number of Electrons Number of Neutrons
11. Hydrogen-1
1
12.
3
1
1
H
8
13.
10
14. Copper-65
15.
0
36
235
92
Chemistry: Matter and Change
U
2
Chapter Assessment
Name ____________________________________________
Date ____________________
Class ___________________
4
Understanding Main Ideas (Part B)
For each description in Column A, write the letter of the matching symbol in Column B.
Column A
Column B
a.
17
8
b.
63
29
Cu
c.
12
6
6C
______ 4. Isotope that has one neutron more than its number of protons
d.
50
24
Cr
______ 5. Carbon with equal numbers of neutrons, protons, and electrons
e.
14
6
C
______ 6. Carbon with two more neutrons than its number of protons
f.
65
29
Cu
______ 7. Chromium with two more neutrons than its number of protons
g.
52
24
Cr
______ 8. Isotope in which the difference between the neutrons and number of protons is 4
h.
54
24
Cr
______ 1. Isotope in which the number of neutrons is six more than
the isotope’s atomic number
______ 2. Copper-63
______ 3. Copper with seven neutrons more than its atomic number
O
Answer the following questions.
9. Calculate the atomic mass of gallium (Ga). Gallium has two isotopes: 69Ga and 71Ga. 69Ga has a
relative abundance of 60.12% and an atomic mass of 68.9257 amu. 71Ga has a relative abundance of
39.88% and an atomic mass of 70.9249 amu. Show all your work.
10. Calculate the atomic mass of the element X. Then use the periodic table to identify the element.
Show all your work.
Isotope
Mass (amu)
Percent Abundance
27
27.977
92.23
28
28.976
4.67
29
29.974
3.10
X
X
X
Chemistry: Matter and Change
3
Chapter Assessment
Name ____________________________________________
Date ____________________
Class ___________________
4
Thinking Critically
Antimony (Sb) has two stable isotopes. 121Sb has a mass of 120.90 amu. 123Sb has a mass of 122.90 amu.
1. What is antimony’s atomic mass? Use the periodic table.
______________________________________________________________________________________________
2. Write an equation to describe the relationship between the percent abundance of 121Sb and the
percent abundance of 123Sb. Assume that no other isotopes exist.
______________________________________________________________________________________________
3. Write an equation that you can use to calculate the percent abundance of each isotope.
______________________________________________________________________________________________
______________________________________________________________________________________________
4. Calculate the percent abundance for each isotope of antimony. Show all your work.
Chemistry: Matter and Change
4
Chapter Assessment
Name ____________________________________________
Date ____________________
Class ___________________
4
Applying Scientific Methods
Data Table I is a chemist’s record of data about six isotopes.
Data Table I
Isotope
Number of Protons
Number of Electrons
Number of Neutrons
Mass (amu)
Isotope 1
24
24
26
49.946
Isotope 2
24
24
28
51.941
Isotope 3
26
26
30
55.999
Isotope 4
24
24
29
52.941
Isotope 5
24
24
30
53.939
Isotope 6
26
26
31
56.969
1. Which of the isotopes listed are the same element? Explain your reasoning.
______________________________________________________________________________________________
______________________________________________________________________________________________
______________________________________________________________________________________________
______________________________________________________________________________________________
2. Explain why the mass of each isotope is not a whole number.
______________________________________________________________________________________________
______________________________________________________________________________________________
______________________________________________________________________________________________
______________________________________________________________________________________________
______________________________________________________________________________________________
Upon further research, the chemist determined the percent abundance of each isotope. These are listed in
Data Table II below.
Data Table II
Isotope
Isotope 1
Isotope 2
Isotope 3
Isotope 4
Isotope 5
Isotope 6
Chemistry: Matter and Change
Percent Abundance
4.35
83.80
81.32
9.50
2.35
18.68
5
Chapter Assessment
Name ____________________________________________
Date ____________________
Class ___________________
4
Applying Scientific Methods, continued
3. Assume that Isotope 1 is an isotope of element X and that all the isotopes of X are listed in Data
Table II. Determine the atomic mass of X. Show all your work.
4. Which isotope of X is most abundant? Least abundant?
______________________________________________________________________________________________
______________________________________________________________________________________________
5. Which isotope of X has the greatest effect on the atomic mass of X? Explain why.
______________________________________________________________________________________________
______________________________________________________________________________________________
______________________________________________________________________________________________
______________________________________________________________________________________________
______________________________________________________________________________________________
6. If the chemist later discovered the following isotope, what could you conclude?
Isotope
Number of Protons
Number of electrons
Number of Neutrons
Mass (amu)
Isotope 7
24
24
31
54.939
______________________________________________________________________________________________
______________________________________________________________________________________________
______________________________________________________________________________________________
______________________________________________________________________________________________
______________________________________________________________________________________________
______________________________________________________________________________________________
______________________________________________________________________________________________
______________________________________________________________________________________________
______________________________________________________________________________________________
______________________________________________________________________________________________
Chemistry: Matter and Change
6
Chapter Assessment
TEACHER GUIDE AND ANSWERS
Chapter Assessment - Chapter 4 — The
Structure of the Atom
Understanding Main Ideas (Part B)
1. h
2. b
3. f
4. a
5. c
6. e
7. d
8. g
9. Mass contribution  (mass)(percent abundance)
69
Ga: (68.9257 amu)(60.12%)  41.44 amu
71
Ga: (70.9249 amu)(39.88%)  28.28 amu
Atomic mass of Ga  41.44 amu  28.28 amu  69.72
amu
10. Mass contribution  (mass)(percent abundance)
For 27X: (27.977 amu)(92.23%)  25.80 amu
For 28X: (28.976 amu)(4.67%)  1.35 amu
For 29X: (29.974 amu)(3.10%)  0.929 amu
Atomic mass of X  25.80 amu  1.35 amu  0.929
amu  28.08 amu
The element is silicon.
Reviewing Vocabulary
1. g
2. d
3. e
4. a
5. c
6. b
7. f
8. i
9. h
10. k
11. m
12. j
13. l
14. Both pertain to atoms. The mass number is the sum of
the protons and neutrons in the nucleus of a given
atom. The atomic number is the number of protons in
an atom.
15. Both concern changes in atoms. A nuclear reaction
involves a change in an atom’s nucleus. A nuclear
equation shows the atomic number and mass number
of the particles involved in a reaction.
Thinking Critically
1. 121.760 amu
2. Percent abundance of 121Sb  Percent abundance of
123
Sb  100%, or 1
3. Atomic mass of Sb  (mass of 121Sb)(percent
abundance of 121Sb)  (mass of 123Sb)(percent
abundance of 123Sb)
4. Assume:
Percent abundance of 121Sb  x
Percent abundance of 123Sb  1 – x
Then solve:
Atomic mass of Sb  121.760 amu  (120.90 amu)x 
(122.90 amu)(1  x)  120.90x amu  122.90 amu
122.90x amu
1.140 amu  2x amu
x  0.570
Percent abundance of 121Sb  57.0%
Percent abundance of 123Sb  1  x  1 0.570 
43.0%
Understanding Main Ideas (Part A)
1. terbium
2. platinum
3. ruthenium
4. chromium
5. scandium
6. cesium
7. neutrons
8. true
9. Alpha
10. neutrons
1
1
H
12. Hydrogen-3, 1, 1, 2
13. Oxygen-18, 188 O, 8
11.
65
29
Cu, 29, 29
15. Uranium-235, 92, 92, 143
14.
Chemistry: Matter and Change
7
Teacher Guide and Answers
TEACHER GUIDE AND ANSWERS
Applying Scientific Methods
1. Isotopes 1, 2, 4, and 5 are the same element; they all
have 24 protons. Isotopes 3 and 6 are another
element; they both have 26 protons.
2. Answers may vary. Although the masses of protons
and neutrons, which make up most of the mass of an
atom, are very close to 1 amu, they are not exactly 1
amu. Thus, the mass of each isotope is very close to a
whole number, but is not exactly a whole number.
3. Mass contribution  (mass)(percent abundance)
Isotope 1: (49.946 amu)(4.35%)  2.17 amu
Isotope 2: (51.941 amu)(83.80%)  43.53 amu
Isotope 4: (52.941 amu)(9.50%)  5.03 amu
Isotope 5: (53.939 amu) (2.35%)  1.27 amu
Atomic mass of X  2.17 amu  43.53 amu  5.03
amu  1.27 amu  52.00 amu
4. Isotope 2; Isotope 5
5. Isotope 2; because the atomic mass of an element is a
weighted average, the isotope that is the most
abundant generally has the greatest effect on the
atomic mass of the element.
6. Answers will vary. Students should include in their
conclusions that Isotope 7, because it has 24 protons,
is an isotope of element X. They may also conclude
that the percent abundance of each isotope of X in
Data Table II and the atomic mass of X calculated in
question 3 may be inaccurate if Isotope 7 occurs in
more than a trace amount. Students may suggest that
the atomic mass of X should be greater than the
calculation in question 3 suggests. Accept all other
reasonable conclusions based on the data provided.
Chemistry: Matter and Change
8
Teacher Guide and Answers