7th Grade- Chapter 3 Online Review

7th Grade - Chapter 3 ONLINE REVEIW

True/False
Indicate whether the statement is true or false.

____ 1. A proton is a positively charged particle present in the nucleus of all atoms.

____ 2. The mass of a proton is much greater than the mass of a neutron.

____ 3. Atoms of the same element can have a different number of neutrons.

____ 4. Dalton believed that the atom was a hard sphere that was the same throughout.

____ 5. J. J. Thomson did experiments that showed that atoms cannot be divided into smaller particles.

____ 6. Rutherford’s experiment showed that alpha particles could pass through foil because most of an atom is neutrally charged.

____ 7. The strong nuclear force can hold the protons of an atom together only if the protons are far apart.

____ 8. Once a living organism dies, the amount of carbon-14 cannot be replaced.

Modified True/False
Indicate whether the statement is true or false. If false, change the identified word or phrase to make the statement true.

____ 9. The idea of the atom was first proposed by Dalton. _________________________

____ 10. An element can be identified by the number of protons in its nucleus. _________________________

____ 11. When an atom's atomic number increases during transmutation the atom has emitted a beta particle. _________________________

____ 12. The mass of an electron is about equal to the mass of a proton. _________________________

____ 13. The mass number of an element can be used to determine the number of electrons in an atom. _________________________

____ 14. Half-life is a measure of the rate of decay of an isotope. _________________________

____ 15. The number of electrons in an atom must equal the number of neutrons. _________________________

____ 16. Except for hydrogen-1, the atomic number of an isotope is always greater than the mass number. _________________________

Multiple Choice
Identify the choice that best completes the statement or answers the question.

____ 17. Why were early philosophers’ theories about life considered only theories?
a.
People had other ideas that were more sensible.
b.
Philosophers had no evidence or proof to back up the theories.
c.
Philosophers would not share their proof with the public.
d.
Scientists did not take philosophers seriously.


____ 18. Which is NOT an example of an element?
a.
carbon
b.
gold
c.
silver
d.
sodium chloride


____ 19. Scientists often revise older scientific theories and models to account for new information. Which scientist revised his own hypothesis about the atom to account for the existence of a nucleus and proton?
a.
William Crookes
b.
John Dalton
c.
Ernest Rutherford
d.
J. J. Thompson


____ 20. Which is the most current scientific model of the atom?
a.
alpha particle model
b.
electron as wave model
c.
electron cloud model
d.
Thompson’s atomic model


____ 21. Sonal made a time line of atomic research and discovery.


How many years passed between Rutherford’s first discoveries about the atom and his first atomic model?
a.
10
b.
14
c.
19
d.
35


____ 22. What does an element’s atomic number represent?
a.
the mass of an one atom of an element
b.
the number of isotopes in the nucleus of one of its atoms
c.
the number of neutrons in the nucleus of one of its atoms
d.
the number of protons in the nucleus of one of its atoms


____ 23. Which two numbers do you need to know in order to find the number of neutrons in an isotope?
a.
atomic number and mass number
b.
atomic number and number of protons
c.
mass number and number of electrons
d.
number of protons and number of electrons


____ 24. In which type of atomic nucleus is radioactive decay most likely?
a.
nucleus with the highest mass number
b.
stable nucleus
c.
transmutated nucleus
d.
unstable nucleus with the lowest mass number


____ 25. Why would an element’s atomic number change after transmutation?
a.
It has added an alpha particle.
b.
It has expelled an alpha particle.
c.
It is no longer an isotope.
d.
It has changed into an isotope.


____ 26. Jerry is using a calendar to figure out how long an 8 g sample of iodine-131 will take to decay. It has a half life of 8 days.


If Jerry starts his experiment on March 1, on which day will he have only 1 g of iodine-131 left?
a.
March 9
b.
March 12
c.
March 25
d.
March 31


____ 27. Why would an archaeologist find it useful to know how much of the element carbon-14 is in a fossil?
a.
They can figure out how much uranium is in the fossil.
b.
They can calculate half-lives of other elements in the fossil.
c.
They can use the half life of carbon-14 to calculate when the animal lived.
d.
They can infer the size of the animal when it died.


____ 28. Which of the following is NOT a use of isotopes?
a.
to detect tumors in the body
b.
to diagnose thyroid problems in humans
c.
to store radioactive waste
d.
to tell how plants use phosphorus to grow


____ 29. Why can’t a geologist use carbon dating to find the age of a rock?
a.
Carbon-14 can only be found in things that were once alive.
b.
Carbon-14 has a different half life when found in rock.
c.
Rocks become radioactive after carbon dating.
d.
Rocks erode too quickly to perform the test.


____ 30. If two atoms have the same number of protons but different numbers of neutrons, they will have the same ____.
a.
half-life
c.
atomic number
b.
mass number
d.
degree of stability


____ 31. If an isotope has an atomic number of 25, which of the following is most likely to be its mass number?
a.
25
c.
75
b.
50
d.
100


____ 32. During beta-particle emission, a neutron splits into ____.
a.
a proton and an electron
c.
two electrons
b.
two protons
d.
two neutrons


____ 33. For a radioactive substance, half-life is determined by ____.
a.
the mass of a given sample
b.
the temperature at which the substance is stored
c.
the presence of magnetic fields
d.
none of the above


____ 34. Which particles have almost the same mass?
a.
proton and electron
c.
electron and neutron
b.
proton and neutron
d.
all three particles


____ 35. Which item best represents Dalton’s mental image of an atom?
a.
a cork
c.
a marble
b.
a candy bar with nuts
d.
a balloon full of air


____ 36. Which item best represents Thomson’s mental image of an atom?
a.
a sponge
c.
a bowling ball
b.
a chocolate-chip cookie
d.
a beach ball


____ 37. Based on his experiment, Rutherford concluded that atoms were ____.
a.
dense positively charged particles
b.
uniform throughout
c.
mainly empty space
d.
made of protons, neutrons, and electrons


____ 38. Which type of particle would NOT be deflected by a magnetic field?
a.
beta particle
c.
proton
b.
alpha particle
d.
neutron


____ 39. A transmutation involving the release of alpha particles produces atoms whose atomic number has ____.
a.
decreased by 2
c.
decreased by 1
b.
increased by 2
d.
increased by 1


____ 40. A transmutation involving the release of beta particles produces atoms whose atomic number has ____.
a.
decreased by 2
c.
decreased by 1
b.
increased by 2
d.
increased by 1


____ 41. The fluorescent screen in Rutherford’s experiment was designed to ____.
a.
detect charged particles
c.
deflect charged particles
b.
attract charged particles
d.
repel charged particles


____ 42. The nucleus is held together by ____.
a.
magnetic attraction
c.
atomic glue
b.
gravity
d.
the strong nuclear force


____ 43. A 10-g sample from a healthy 200-year-old redwood would contain ____ carbon-14 as a 10-g sample from a 20-year-old redwood sapling.
a.
one-tenth as much
c.
twice as much
b.
the same amount of
d.
half as much


____ 44. Which of the following properties of iodine-131 make it a good choice as a tracer element?
a.
It is absorbed equally by all cells in the body.
b.
It is absorbed mainly by cells in the thyroid.
c.
It has a relatively long half-life.
d.
It is a normally stable isotope.


____ 45. ____ contain(s) only one kind of atom.
a.
Matter
c.
Chemicals
b.
Elements
d.
Radioactive materials


____ 46. A(n) ____ is the basic unit of matter.
a.
electron
c.
atom
b.
molecule
d.
space


____ 47. Particles in an atom’s nucleus that do not have an electric charge are called ____.
a.
neutrons
c.
ions
b.
electrons
d.
protons


____ 48. The atomic mass of an atom consists of the mass of the ____.
a.
protons and neutrons
c.
neutrons and electrons
b.
protons and electrons
d.
neutrons, protons, and electrons


____ 49. In an atom, the electrons can be found in the ____.
a.
nucleus
c.
isotope
b.
neutron
d.
electron cloud


____ 50. J. J. Thomson used the fact that ____ charges attract each other in his cathode-ray tube experiment.
a.
like
c.
atomic
b.
neutral
d.
opposite


____ 51. The mass number of an isotope is the number of ____.
a.
electrons and protons
c.
neutrons
b.
neutrons and protons
d.
protons


____ 52. Isotopes are atoms of the same element that have a different number of ____.
a.
protons
c.
neutrons
b.
electrons
d.
nuclei


____ 53. To find the number of neutrons in an isotope, subtract the____.
a.
atomic number from the mass number
b.
mass number from the atomic number
c.
number of isotopes from the mass number
d.
number of protons from the number of electrons


____ 54. The most stable isotope of an atom with 12 protons probably has ____ neutrons.
a.
24
c.
6
b.
18
d.
12


____ 55. The strong nuclear force holds the ____ together.
a.
protons
c.
nucleus
b.
neutrons
d.
electrons


____ 56. Radioactive decay is the release of ____.
a.
radios
c.
nuclear particles and energy
b.
isotopes
d.
light


____ 57. A(n) ____ particle consists of two protons and two neutrons.
a.
gamma
c.
beta
b.
alpha
d.
omega


____ 58. The changing of one element into another in radioactive decay is called ____.
a.
transmutation
c.
half-life
b.
radiation
d.
a chain reaction


____ 59. Radioactive decay can be affected by ____.
a.
the weather
c.
increased pressure
b.
magnetic fields
d.
none of these


____ 60. A radioactive isotope has a half-life of 100 years. A sample of 40 g of the isotope will have a mass of ____ g in 200 years.
a.
120
c.
20
b.
40
d.
10


____ 61. Tracer elements can be used without danger to people because they have ____ half-lives.
a.
short
c.
strong
b.
long
d.
nonexistent


Completion
Complete each statement.

62. Most of the mass of an atom is located in its ____________________.

63. Atoms that are unstable are more likely to be ____________________ than atoms that are stable.

64. The high-energy electrons given off during radioactive decay are called ____________________.

65. Of the three main subatomic particles, the ____________________ has the least mass.

66. The type of glass tube that Crookes and Thomson used for their experiments is called a(n) ____________________ tube.

67. The stream of particles in a cathode-ray tube travels from the cathode to the ____________________.

68. The likely location of the negatively charged particles in an atom is called a(n) ____________________.

69. Atoms of the same element containing different numbers of neutrons are called ____________________.

Complete the following sentences using the terms listed below. Some terms may not be used.

atoms
anode
predictable
cathode
sphere
cloud
random
tracer elements
archaeology
chemistry


70. The study of matter is called ____________________.

71. Different elements are made up of different kinds of ____________________.

72. A(n) ____________________ is an electrode that has a positive charge.

73. A(n) ____________________ is an electrode that has a negative charge.

74. An electron cloud is shaped like a(n) ____________________ with the nucleus at its center.

75. Radioactive decay is a(n) ____________________ process.

76. Isotopes called ____________________ are used to diagnose disease and to study environmental conditions.

Choose the best of the three choices in parentheses.

77. The Greeks named what they believed to be the tiniest particle of matter a(n) ____________________ (proton, atom, cell).

78. An element is made up of only one kind of ____________________ (isotope, atom, particle).

79. Research using ____________________ (television, atomic bombs, cathode rays) led scientists to believe that the atom could be broken down into smaller particles.

80. A(n) ____________________ (electron, proton, neutron) is electrically neutral.

81. An atomic nucleus is often most stable if the number of protons is ____________________ (equal to, greater than, less than) the number of neutrons.

82. Atoms of the same element always have the same number of ____________________ (neutrons, electrons, protons).

83. To find the number of neutrons in an isotope, start with the mass number and ______________________________ (add the atomic number, subtract the atomic number, multiply by two).

84. If you have 16 g of a substance that has a half-life of 3 days, after 12 days you will have ____________________ (8, 1, 0) g of the substance remaining.

Matching

Match each isotope with the correct statement below.
a.
carbon-14
c.
iodine-131
b.
americium-241
d.
phosphorus-32


____ 85. used to study plant growth and reproduction

____ 86. used to determine the age of once-living artifacts

____ 87. used in the diagnosis of thyroid disease

____ 88. used in many smoke detectors

Match each scientist with the correct statement below.
a.
Thomson
c.
Crookes
b.
Dalton
d.
Rutherford


____ 89. Almost all the mass of an atom is located in its nucleus.

____ 90. Different elements are made of different types of atoms.

____ 91. Cathode rays are made up of negatively charged particles.

____ 92. used the cathode-ray tube to discover streams of particles

Match each item with the correct description below.
a.
neutron
h.
half-life
b.
mass number
i.
isotopes
c.
atomic number
j.
transmutation
d.
element
k.
alpha particle
e.
beta particle
l.
proton
f.
electron cloud
m.
radioactive decay
g.
electron
n.
average atomic mass


____ 93. matter that is made up of only one kind of atom

____ 94. a negatively charged particle that is part of every kind of matter

____ 95. a positively charged particle that is present in the nucleus of all atoms

____ 96. uncharged particle in the nucleus of an atom

____ 97. region surrounding the nucleus in which the electrons move about

____ 98. the number of protons in the nucleus of an atom of an element

____ 99. atoms of the same element that have different numbers of neutrons

____ 100. the number of neutrons plus protons in the nucleus of an atom

____ 101. the mass of the mixture of the isotopes for an element

____ 102. the release of nuclear particles and energy

____ 103. the changing of one element into another element through radioactive decay

____ 104. particle consisting of two protons and two neutrons

____ 105. a high-energy electron that comes from the nucleus, not from the electron cloud

____ 106. the amount of time required for half a sample of a radioactive isotope to decay

Short Answer

107.
Why do you think the electron cloud theory is the current and accepted model of the atom and how it works?

108.
It took many years and the work of many scientists to discover how atoms work.

Part A Explain why scientific collaboration and use of other scientific theories is important for the advancement of science and the development of human culture.

Part B Explain what further research about atoms and atomic theories can do for the advancement of science and human culture.

109.
Use Thomson’s cathode-ray experiments to explain why the neutron was the last of the three main subatomic particles to be discovered.

110.
Explain why an isotope with a half-life of 7 years would not be a good choice for a tracer element used to diagnose illnesses.

111.
Name three key differences between beta particles and ordinary electrons.

112.
Dalton thought that all the atoms of an element were identical. Based on what you have learned, how would you modify Dalton’s definition of an element?

113.
The model of the atom proposed by Greek philosophers appears similar to the model proposed centuries later by Dalton. What was the key difference between the two models?

114.
One isotope of helium is called helium-4. Knowing that helium has an atomic number of 2, explain why an alpha particle is sometimes referred to as a helium nucleus.

115.
How would the results of Rutherford’s metal foil experiment have been different if he had bombarded the foil with beta particles instead of alpha particles?

116.
Could carbon-14 be used to date a stone arrowhead found at an ancient burial site? Explain your reasoning.

117.
Where do the stream of particles in a cathode-ray tube come from? What provides the energy for their release?

118.
Explain why the mass of electrons can be ignored when the mass number of an atom is calculated.

119.
Suppose a scientist wants to isolate the isotopes of hydrogen (hydrogen-1, hydrogen-2, and hydrogen-3) from a sample of hydrogen. What property of the isotopes would the scientist need to rely on when designing a separation method?

120.
Suppose you had a 2-g sample of carbon-14 and a 2-g sample of iodine-131. If you used a Geiger counter to measure radioactive decay, which sample would show the larger initial rate of decay? Give a reason for your answer. How would the rates of decay change over a period of a week?

121.
Americium-241, which is used in home smoke detectors, has a half-life of about 400 years, yet manufacturers recommend discarding home smoke detectors after ten years. Could a homeowner install a smoke detector containing americium-241 and use it for decades if he or she replaces the battery once a year?

122.
The elements with atomic numbers 43 and 61 (technetium and promethium) are the only two of the elements from atomic number 1 to atomic number 83 that cannot be found in nature. What can you infer about the isotopes of technetium and promethium? Could these elements have existed in nature when Earth was first formed?

123.
The scientists who developed the modern theory of atomic structure never saw an atom. In general, on what did they base their theories?

124.
Carbon-14 dating cannot be used for nonliving materials or for materials that are older than about 50,000 years. Propose a related method scientists could use to date older, nonliving materials.

125.
Make a sketch of the solar system showing the Sun and the planets. Use the sketch to draw an analogy between the solar system and the structure of an atom. How are the two systems similar? How are they different?

Number of Subatomic Particles in Selected Isotopes
Isotope
Number of protons
Number of neutrons
Number of electrons
magnesium-24


12
magnesium-26
12


chlorine-35

18

chlorine-37


17
Table 14-1

126.
Use what you know about atomic structure to fill in the missing data in Table 14-1.

127.
Propose a model of matter that explains how atoms, which contain so much empty space, can combine to form materials such as a copper pipe or an aluminum pan that appear so solid.

128.
Suppose you were constructing a time line of developments that contributed to the modern model of the atom. Place the following events in the order that they would appear on the time line. Begin with the earliest event.
______ a. Thomson’s evidence for the existence of positive particles in atoms
______ b. Rutherford’s metal foil experiment
______ c. discovery of the neutron
______ d. the description of an atom as the smallest particle of matter
______ e. Crookes' experiments with the cathode-ray tube

129. Study the following diagram. Then label each part using the correct terms from the list.

electron
electron cloud
neutron
nucleus
proton


Use your knowledge of atomic structure to answer the following questions.


Atom
Number of protons
Number of neutrons
Number of electrons
Atomic number
Mass number
a
6

6

12
b

0
1
1

c
11

11

23
d

8
6
6

e
17

17

35
f
12
12
12


g

10
9
9



130. What are the missing values from the table?

131. Which two are isotopes of one another? Explain why they are isotopes.

132. Which two atoms could be the “before” and “after” of an alpha ejection?

133. Which atom could not possibly emit an alpha particle? Why?

134. In an outline, the subtopics are neutron, proton, and electron. What is the main topic?

135. In an outline, the subtopics are fossil dating, cancer detection, and circulation problems. What is the main topic?

136. An atom has a mass number of 53 and an atomic number of 26. How many neutrons does it have? Include a formula that explains your calculation.

137. The isotopes of carbon (carbon-12, carbon-13, and carbon-14) have different mass numbers. Each isotope has six protons. Explain how you can determine the number of neutrons in each isotope.

138. A certain element has a half-life of 20 years. A scientist starts with 100 g of the element.
a. How many grams remain after 20 years?
b. How many grams remain after 40 years?
c. How many half-lives are there in a 100-year span? How many grams of the sample would remain at the end of the 100 years?

Problem

Figure 14-1

139.
Figure 14-1 shows the decay of a sample of neptunium-238 over a period of 10 days. What is the half-life of neptunium-238?

140.
If the original sample in Figure 14-1 contains 0.620 g, how much neptunium-238 will remain after 4 days? How much will remain after 8 days?

141.
Uranium is the element with atomic number 92. Uranium-235 is a radioactive isotope that decays by emitting alpha particles. What is the atomic number of the new element that forms? What is its mass number?

142.
Thorium is the element with atomic number 90. Thorium-231 is a radioactive isotope that decays by emitting beta particles. What is the atomic number of the new element that forms? What is its mass number?

Essay

143. How is americium-241 used in smoke detectors?
7th Grade - Chapter 3 ONLINE REVEIW
Answer Section

TRUE/FALSE

1. ANS: T PTS: 1

2. ANS: F PTS: 1

3. ANS: T PTS: 1

4. ANS: T PTS: 1

5. ANS: F PTS: 1

6. ANS: F PTS: 1

7. ANS: F PTS: 1

8. ANS: T PTS: 1

MODIFIED TRUE/FALSE

9. ANS: F, ancient Greeks

PTS: 1 DIF: Webb's I OBJ: 2/1 STA: SC.H.1.3.6 SC.H.3.3.5

10. ANS: T PTS: 1 DIF: Webb's I
OBJ: 3/1 STA: SC.A.1.3.1 SC.A.2.3.2

11. ANS: T PTS: 1 DIF: Webb's I
OBJ: 5/2 STA: SC.A.2.3.2

12. ANS: F, neutron

PTS: 1 DIF: Webb's I OBJ: 3/1 STA: SC.A.2.3.2

13. ANS: F, atomic number

PTS: 1 DIF: Webb's I OBJ: 3/1 STA: SC.A.2.3.2

14. ANS: T PTS: 1 DIF: Webb's I
OBJ: 5/2

15. ANS: F, protons

PTS: 1 DIF: Webb's I OBJ: 3/1 STA: SC.A.2.3.2

16. ANS: F, less

PTS: 1 DIF: Webb's I OBJ: 3/1 STA: SC.A.2.3.2

MULTIPLE CHOICE

17. ANS: B PTS: 1 DIF: Webb's II STA: SC.H.1.3.1

18. ANS: D PTS: 1 DIF: Webb's I STA: SC.A.1.3.1

19. ANS: C PTS: 1 DIF: Webb's I STA: SC.H.1.3.1

20. ANS: C PTS: 1 DIF: Webb's I STA: SC.H.1.3.1 SC.A.2.3.2

21. ANS: B PTS: 1 DIF: Webb's II
STA: SC.H.1.3.1 SC.H.1.3.6 SC.H.3.3.5

22. ANS: D PTS: 1 DIF: Webb's I STA: SC.A.2.3.2

23. ANS: A PTS: 1 DIF: Webb's I STA: SC.A.2.3.2

24. ANS: D PTS: 1 DIF: Webb's II STA: SC.A.2.3.2

25. ANS: B PTS: 1 DIF: Webb's II STA: SC.A.2.3.2

26. ANS: C PTS: 1 DIF: Webb's II STA: SC.A.2.3.2 SC.D.1.3.5

27. ANS: C PTS: 1 DIF: Webb's II STA: SC.A.2.3.2 SC.D.1.3.5

28. ANS: C PTS: 1 DIF: Webb's I

29. ANS: A PTS: 1 DIF: Webb's II STA: SC.A.1.3.1

30. ANS: C PTS: 1 DIF: Webb's I OBJ: 3/1
STA: SC.A.2.3.2

31. ANS: B PTS: 1 DIF: Webb's I OBJ: 3/1

32. ANS: A PTS: 1 DIF: Webb's I OBJ: 5/2
STA: SC.A.2.3.2

33. ANS: D PTS: 1 DIF: Webb's I OBJ: 5/2

34. ANS: B PTS: 1 DIF: Webb's I OBJ: 3/1
STA: SC.A.2.3.2

35. ANS: C PTS: 1 DIF: Webb's I OBJ: 2/1
STA: SC.H.1.3.1 SC.H.1.3.6

36. ANS: B PTS: 1 DIF: Webb's I OBJ: 2/1
STA: SC.H.1.3.1 SC.H.1.3.6

37. ANS: C PTS: 1 DIF: Webb's I OBJ: 2/1
STA: SC.H.1.3.1 SC.H.1.3.6

38. ANS: D PTS: 1 DIF: Webb's II OBJ: 1/1
STA: SC.A.2.3.1 SC.A.2.3.2

39. ANS: A PTS: 1 DIF: Webb's I OBJ: 5/2
STA: SC.A.2.3.2

40. ANS: D PTS: 1 DIF: Webb's I OBJ: 5/2
STA: SC.A.2.3.2

41. ANS: A PTS: 1 DIF: Webb's I OBJ: 1/1
STA: SC.H.1.3.1 SC.H.1.3.6

42. ANS: D PTS: 1 DIF: Webb's I OBJ: 3/1
STA: SC.A.2.3.2

43. ANS: B PTS: 1 DIF: Webb's I OBJ: 5/2

44. ANS: B PTS: 1 DIF: Webb's I OBJ: 6/2

45. ANS: B PTS: 1

46. ANS: C PTS: 1

47. ANS: A PTS: 1

48. ANS: A PTS: 1

49. ANS: D PTS: 1

50. ANS: D PTS: 1

51. ANS: B PTS: 1

52. ANS: C PTS: 1

53. ANS: A PTS: 1

54. ANS: D PTS: 1

55. ANS: C PTS: 1

56. ANS: C PTS: 1

57. ANS: B PTS: 1

58. ANS: A PTS: 1

59. ANS: D PTS: 1

60. ANS: D PTS: 1

61. ANS: A PTS: 1

COMPLETION

62. ANS: nucleus

PTS: 1 DIF: Webb's I OBJ: 3/1 STA: SC.A.2.3.2

63. ANS: radioactive

PTS: 1 DIF: Webb's I OBJ: 4/1 STA: SC.A.2.3.2

64. ANS: beta particles

PTS: 1 DIF: Webb's I OBJ: 4/1 STA: SC.A.2.3.2

65. ANS: electron

PTS: 1 DIF: Webb's I OBJ: 3/1 STA: SC.A.2.3.2

66. ANS: cathode-ray

PTS: 1 DIF: Webb's I OBJ: 1/1 STA: SC.H.1.3.6

67. ANS: anode

PTS: 1 DIF: Webb's I OBJ: 1/1

68. ANS: electron cloud

PTS: 1 DIF: Webb's I OBJ: 3/1 STA: SC.A.2.3.2

69. ANS: isotopes

PTS: 1 DIF: Webb's I OBJ: 5/2 STA: SC.A.2.3.2

70. ANS: chemistry

PTS: 1

71. ANS: atoms

PTS: 1

72. ANS: anode

PTS: 1

73. ANS: cathode

PTS: 1

74. ANS: sphere

PTS: 1

75. ANS: random

PTS: 1

76. ANS: tracer elements

PTS: 1

77. ANS: atom

PTS: 1

78. ANS: atom

PTS: 1

79. ANS: cathode rays

PTS: 1

80. ANS: neutron

PTS: 1

81. ANS: equal to

PTS: 1

82. ANS: protons

PTS: 1

83. ANS: subtract the atomic number

PTS: 1

84. ANS: 1

PTS: 1

MATCHING

85. ANS: D PTS: 1 DIF: Webb's I OBJ: 6/2

86. ANS: A PTS: 1 DIF: Webb's I OBJ: 6/2

87. ANS: C PTS: 1 DIF: Webb's I OBJ: 6/2

88. ANS: B PTS: 1 DIF: Webb's I OBJ: 6/2

89. ANS: D PTS: 1 DIF: Webb's I OBJ: 2/1
STA: SC.A.2.3.2

90. ANS: B PTS: 1 DIF: Webb's I OBJ: 2/1
STA: SC.A.2.3.2

91. ANS: A PTS: 1 DIF: Webb's I OBJ: 1/1
STA: SC.A.2.3.1 SC.A.2.3.2

92. ANS: C PTS: 1 DIF: Webb's I OBJ: 1/1
STA: SC.A.2.3.1 SC.A.2.3.2

93. ANS: D PTS: 1

94. ANS: G PTS: 1

95. ANS: L PTS: 1

96. ANS: A PTS: 1

97. ANS: F PTS: 1

98. ANS: C PTS: 1

99. ANS: I PTS: 1

100. ANS: B PTS: 1

101. ANS: N PTS: 1

102. ANS: M PTS: 1

103. ANS: J PTS: 1

104. ANS: K PTS: 1

105. ANS: E PTS: 1

106. ANS: H PTS: 1

SHORT ANSWER

107. ANS:
The theory accounts for recent research that explains the unpredictable nature of electrons. The behavior of electrons is more comparable to that of waves than of particles. Electrons are also more likely to be found close to the nucleus because they are attracted to the positive charges of the protons. The electrons in the region surrounding the nucleus create a cloud-like appearance, which explains the name “electron cloud model.”

PTS: 1 DIF: Webb's II STA: SC.A.2.3.2 SC.H.1.3.1

108. ANS:
Part A Answers will vary, but may include the idea that scientific theories often build on each other over time. For example, one scientist may make discoveries about protons, enabling another group of scientists to do further research. Further research may uncover information about neutrons or other related information. This helps advance science and human culture by providing people with more general knowledge about life.

Part B Further exploration about atoms and atomic theories enables general scientific knowledge to increase. It also allows for possible cures for diseases and can save many lives.

PTS: 1 DIF: Webb's III STA: SC.H.1.3.6 SC.H.3.3.5

109. ANS:
Thomson used magnetic fields to detect charged particles in his cathode-ray tube. Because neutrons have no charge, the cathode-ray tube did not detect them.

PTS: 1 DIF: Webb's II OBJ: 1/1 STA: SC.H.1.3.1 SC.H.1.3.6

110. ANS:
A small quantity of the isotope would not decay quickly enough to produce the desired effect, if the isotope were absorbed into body tissues, the patient would be exposed to a prolonged and most likely damaging, dose of radiation.

PTS: 1 DIF: Webb's II OBJ: 6/2 STA: SC.A.2.3.3

111. ANS:
Beta particles 1) are emitted from the atom during radioactive decay, 2) originate in the nucleus when a neutron splits into a proton and electron, and 3) have higher energies than ordinary electrons.

PTS: 1 DIF: Webb's II OBJ: 5/2 STA: SC.A.2.3.2

112. ANS:
All atoms of an element are not identical. Many elements have more than one isotope. Although each atom of an element has the same number of protons, the numbers of neutrons in the atom's nucleus can vary.

PTS: 1 DIF: Webb's II OBJ: 2/1
STA: SC.A.2.3.2 SC.H.1.3.1 SC.H.1.3.6

113. ANS:
Dalton’s model was based on scientific research and open to challenge by further studies. The Greeks used logic, but they did not do experiments. Dalton also added the idea of different atoms for different elements.

PTS: 1 DIF: Webb's II OBJ: 2/1 STA: SC.H.1.3.1 SC.H.1.3.6

114. ANS:
An alpha particle consists of two protons and two neutrons, the same four particles as in a helium-4 nucleus (mass number 4 – atomic number 2).

PTS: 1 DIF: Webb's II OBJ: 5/2 STA: SC.A.2.3.2

115. ANS:
The paths of beta particles that passed near the nucleus would have been deflected in a different direction because of the force of attraction between the electrons and protons.

PTS: 1 DIF: Webb's II OBJ: 1/1 STA: SC.A.2.3.2

116. ANS:
No, carbon-14 can be used to date objects that were once alive, not objects like stone that were never alive. An organism had to absorb carbon-14 as a natural part of metabolism so that the decay process could begin when it died.

PTS: 1 DIF: Webb's II OBJ: 5/2

117. ANS:
The stream of particles are emitted by the cathode. The high-voltage electrical source supplies the energy for their release.

PTS: 1 DIF: Webb's II OBJ: 1/1 STA: SC.A.2.3.1

118. ANS:
Protons and neutrons in the nucleus account for almost all the mass of an atom. The electrons are almost without mass and perhaps can be explained as waves rather than particles.

PTS: 1 DIF: Webb's II OBJ: 3/1 STA: SC.A.2.3.2

119. ANS:
The scientist would need to rely on the difference in mass.

PTS: 1 DIF: Webb's II OBJ: 5/2

120. ANS:
The iodine-131 would show the larger initial decay because it has a much shorter half-life. The decay of iodine-131 would drop off dramatically during the week; there would be no noticeable change in decay for the carbon-14 sample.

PTS: 1 DIF: Webb's II OBJ: 6/2

121. ANS:
Theoretically, an isotope with a half-life of 400 years should provide enough alpha particles to allow the smoke detector to work for many more years. However, the sample of americium-241 in the detector may be so small that the number of alpha particles emitted drops below the needed level. Also, the reliability of other parts in the detector may be limited to ten years. The smoke detector should be replaced.

PTS: 1 DIF: Webb's II OBJ: 6/2

122. ANS:
Technetium and promethium have no stable isotopes. These two elements could have existed long ago, but any deposits of these elements have long since decayed.

PTS: 1 DIF: Webb's II OBJ: 5/2

123. ANS:
They based their theories on the observed behavior of atoms and of subatomic particles. For example, they couldn’t see an electron, but they could observe behavior of electrons in a cathode-ray tube. As they learned more about the behavior, they modified their theories.

PTS: 1 DIF: Webb's II OBJ: 2/1 STA: SC.H.1.3.1 SC.H.1.3.3

124. ANS:
Find a radioactive isotope of an element that is commonly found in rocks. The isotope would need to have a long half-life.

PTS: 1 DIF: Webb's II OBJ: 6/2

125. ANS:
Students may compare the Sun and the planets to the nucleus and electrons. The gravitational attraction between the Sun and planets can be compared to the attraction between electrons and protons in the nucleus. There is a lot of empty space in both systems. Unlike electrons, the planets are not identical. In contrast to the electron cloud, the location of the planets in relation to the Sun is definite. Electrons are likely to be close to the nucleus, but they could be anywhere.

PTS: 1 DIF: Webb's III OBJ: 3/1 STA: SC.A.2.3.2 SC.E.1.3.1

126. ANS:

Number of Subatomic Particles in Selected Isotopes
Isotope
Number of protons
Number of neutrons
Number of electrons
magnesium-24
12
12
12
magnesium-26
12
14
12
chlorine-35
17
18
17
chlorine-37
17
20
17


PTS: 1 DIF: Webb's II OBJ: 5/2 STA: SC.A.2.3.2

127. ANS:
Students’ models will probably focus on the large number of atoms and their possible arrangements. One possible analogy could use a chain link fence. With a single layer of fencing, the holes in the fence are obvious and easy to penetrate. With multiple layers placed one on top of the other, the structure becomes more solid and a path through the layers much less direct.

PTS: 1 DIF: Webb's III OBJ: 3/1 STA: SC.A.2.3.2

128. ANS:
D, E, A, B, C

PTS: 1 DIF: Webb's II OBJ: 2/1 STA: SC.H.1.3.6

129. ANS:

PTS: 1

130. ANS:
a. 6, 6
b. 1, 1
c. 12, 11
d. 6, 14
e. 18, 17
f. 12, 24
g. 9, 19

PTS: 1

131. ANS:
Atom a and atom d are isotopes. They have the same atomic number, or number of protons, but different mass numbers because the number of neutrons is different.

PTS: 1

132. ANS:
Atom c could be the “before” of an alpha ejection, and atom g could be the “after.”

PTS: 1

133. ANS:
Atom b, which has one proton and no neutrons, could not possibly emit an alpha particle, which consists of two protons and two neutrons.

PTS: 1

134. ANS:
Answers will vary slightly. Topics should indicate that neutrons, protons, and electrons are particles within atoms.

PTS: 1

135. ANS:
Answers will vary slightly. Topics should indicate uses of radioactive isotopes.

PTS: 1

136. ANS:
number of neutrons = mass number – atomic number
53 – 26 = 27

PTS: 1

137. ANS:
The number of neutrons in an atom, including isotopes of the same element, can be calculated by subtracting the atomic number from the mass number.

For carbon-12: number of neutrons = 12 – 6 = 6
For carbon-13: number of neutrons = 13 – 6 = 7
For carbon-14: number of neutrons = 14 – 6 = 8

PTS: 1

138. ANS:

PTS: 1

PROBLEM

139. ANS:
2 days

PTS: 1 DIF: Webb's II OBJ: 5/2

140. ANS:
0.155 g; 0.0388 g

PTS: 1 DIF: Webb's II OBJ: 5/2

141. ANS:
atomic number = 90; mass number = 231

PTS: 1 DIF: Webb's II OBJ: 5/2 STA: SC.A.2.3.2

142. ANS:
atomic number = 91; mass number = 231

PTS: 1 DIF: Webb's II OBJ: 4/1 STA: SC.A.2.3.2

ESSAY

143. ANS:
Americium-241 undergoes transmutation to neptunium by ejecting an alpha particle. The air in a smoke detector can conduct electricity because of the presence of the alpha particles. As long as the electric current flows, the smoke detector stays silent. If smoke enters the detector, the current is interrupted and the alarm sounds.

PTS: 1