Modified True/False
Indicate
whether the statement is true or false. If false, change the identified word or phrase to make the
statement true.
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1.
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The idea of the atom was first proposed by Dalton.
_________________________
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2.
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An element can be identified by the number of protons in its nucleus.
_________________________
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3.
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When an atom's atomic number increases during transmutation the atom has
emitted a beta particle. _________________________
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4.
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The mass of an electron is about equal to the mass of a proton.
_________________________
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5.
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The mass number of an element can be used to determine the number of
electrons in an atom. _________________________
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6.
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Half-life is a measure of the rate of decay of an isotope.
_________________________
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7.
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The number of electrons in an atom must equal the number of neutrons.
_________________________
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8.
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Except for hydrogen-1, the atomic number of an isotope is always greater
than the mass number. _________________________
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Multiple Choice
Identify the
choice that best completes the statement or answers the question.
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9.
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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 |
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10.
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If an isotope has an atomic number of 25, which of the following is most likely
to be its mass number?
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11.
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During beta-particle emission, a neutron splits into ____.
a. | a proton and an electron | c. | two electrons | b. | two
protons | d. | two
neutrons |
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12.
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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 |
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13.
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Which particles have almost the same mass?
a. | proton and electron | c. | electron and neutron | b. | proton and neutron | d. | all three
particles |
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14.
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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 |
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15.
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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 |
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16.
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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 |
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17.
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Which type of particle would NOT be deflected by a magnetic field?
a. | beta particle | c. | proton | b. | alpha particle | d. | neutron |
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18.
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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 |
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19.
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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 |
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20.
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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 |
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21.
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The nucleus is held together by ____.
a. | magnetic attraction | c. | atomic glue | b. | gravity | d. | the strong nuclear
force |
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22.
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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 |
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23.
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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. |
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Matching
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Match each isotope with the correct statement below. a. | carbon-14 | c. | iodine-131 | b. | americium-241 | d. | phosphorus-32 |
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24.
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used to study plant growth and reproduction
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25.
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used to determine the age of once-living artifacts
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26.
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used in the diagnosis of thyroid disease
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27.
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used in many smoke detectors
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Match each scientist with the correct statement below. a. | Thomson | c. | Crookes | b. | Dalton | d. | Rutherford |
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28.
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Almost all the mass of an atom is located in its nucleus.
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29.
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Different elements are made of different types of atoms.
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30.
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Cathode rays are made up of negatively charged particles.
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31.
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used the cathode-ray tube to discover streams of particles
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Completion
Complete each
statement.
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32.
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Most of the mass of an atom is located in its ____________________.
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33.
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Atoms that are unstable are more likely to be ____________________ than atoms
that are stable.
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34.
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The high-energy electrons given off during radioactive decay are called
____________________.
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35.
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Of the three main subatomic particles, the ____________________ has the least
mass.
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36.
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The type of glass tube that Crookes and Thomson used for their experiments is
called a(n) ____________________ tube.
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37.
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The stream of particles in a cathode-ray tube travels from the cathode to the
____________________.
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38.
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The likely location of the negatively charged particles in an atom is called
a(n) ____________________.
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39.
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Atoms of the same element containing different numbers of neutrons are called
____________________.
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Short Answer
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40.
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Use Thomson’s cathode-ray experiments to explain why the neutron was the
last of the three main subatomic particles to be discovered.
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41.
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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.
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42.
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Name three key differences between beta particles and ordinary electrons.
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43.
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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?
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44.
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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?
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45.
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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.
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46.
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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?
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47.
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Could carbon-14 be used to date a stone arrowhead found at an ancient burial
site? Explain your reasoning.
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48.
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Where do the stream of particles in a cathode-ray tube come from? What provides
the energy for their release?
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49.
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Explain why the mass of electrons can be ignored when the mass number of an atom
is calculated.
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50.
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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?
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51.
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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?
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52.
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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?
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53.
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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?
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54.
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The scientists who developed the modern theory of atomic structure never saw an
atom. In general, on what did they base their theories?
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55.
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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.
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56.
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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?
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57.
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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.
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58.
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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
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Problem
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59.
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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?
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60.
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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?
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