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Chapter 1 Review, pages 48–53
Knowledge
1. (c)
2. (a)
3. (d)
4. (a)
5. (c)
6. (b)
7. (b)
8. (d)
9. (b)
10. True
11. False. The atomic number of an atom is the number of protons it contains.
12. True
13. False. The nitrate ion and the sulfate ion are examples of polyatomic anions.
14. False. You can determine the atomic mass of an element by calculating the weighted average
of the masses of all of its isotopes.
15. True
16. False. Dobereiner arranged groups of three atoms that have similar properties.
17. True
18. False. A metal ion is smaller than the atom from which it formed.
19. (a) (vi)
(b) (iii)
(c) (iv)
(d) (ii)
(e) (i)
(f) (v)
20. Five branches of chemistry are inorganic chemistry, organic chemistry, nuclear chemistry,
biochemistry, and physical chemistry.
21. Science involves acquiring knowledge about matter and its interactions. Technology involves
applying this knowledge to produce something useful.
22. Empirical knowledge is based on observations. Theoretical knowledge is based on using
ideas to explain observations.
23. Thomson saw that a beam of electrons was attracted to a positively charged plate in the tube,
so he concluded that the beam consisted of negatively charged particles.
24. (a) The atomic number of aluminum is 13.
(b) The mass number of this aluminum atom is 27.
25. A substance that is chemically inert does not react with other substances.
26. Polyatomic ions make up bones and teeth and control the pH of the blood.
27. Three possible ways in which an atom can achieve a complete octet are by sharing, losing, or
gaining electrons.
28. A polyatomic ion is a charged entity made up of several atoms.
29. Both nitrate ions and nitrite ions are polyatomic ions made up of a nitrogen atom and oxygen
atoms. Both have a charge of +1. However, a nitrate ion has one more oxygen atom than a nitrite
ion.
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30. (a) Isotopes are atoms of the same element that contain different numbers of neutrons.
(b) Radioisotopes are isotopes whose nuclei decay and produce radiation. Isotopes that are not
radioactive have stable nuclei that do not decay or produce radiation.
31. (a) The isotope emitted an alpha particle.
(b) The mass number was lowered by 4, so a particle with a mass number of 4 (an alpha particle)
must have been emitted.
32. (a)
(b)
(c)
33. (a)
(b)
(c)
(d)
34. (a) A periodic trend is a pattern in properties observed as you move from left to right across a
period.
(b) Periodic law states that periodic trends can be observed when elements are arranged by
increasing atomic number.
35. Elements within a group on the periodic table have the same number of valence electrons.
36. (a) Elements in Groups 1, 2, and 13 to 18 are called representative elements.
(b) These elements are called representative elements because they most closely follow periodic
law.
37. (a) The metals are located on the left side of the periodic table.
(b) The non-metals are located on the right side of the periodic table.
(c) The metalloids are located right next to the zigzag staircase line between metals and nonmetals.
38. (a) Hennig Brand isolated the element phosphorus.
(b) Antoine Lavoisier published a book describing 33 elements and distinguished between metals
and non-metals.
39. The unit usually used to communicate the radius of an atom is the picometre (pm).
40. (a) When an atom gains an electron, energy is usually released.
(b) When an atom loses an electron, energy is absorbed.
41. Electron affinity is the energy change that occurs when an atom in the gaseous state gains an
electron. The quantity of energy released indicates how easily an atom gains an electron.
Understanding
42. (a) Knowledge of the atom is considered to be theoretical knowledge because it has not been
directly observed. The theory changes over time as new information becomes available.
(b) New technology will probably reveal additional subatomic particles or enable scientists to
create theories about additional forces related to the nucleus.
43. (a) The unit most commonly used to measure the mass of an atom is the atomic mass unit, u,
1
which is
the mass of a carbon-12 atom.
2
(b) This unit is used instead because masses of atoms in grams or kilograms would be so small
that the numbers would be cumbersome.
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44. (a) In his gold foil experiment, Rutherford observed that most of the alpha particles passed
through the gold foil unaffected. Some, however, were deflected, and a few actually bounced
back in the direction from which they entered the foil.
(b) Most particles passed through the foil, which meant that the atom was mostly empty space.
The deflected particles were positively charged, which meant that a dense, positively charged
object repelled them. Rutherford proposed that this object was the nucleus, where all the mass
and positive charge of the atom was concentrated.
45. Answers may vary. Sample answers:
(a) Nitrite, NO2–, and nitrate, NO3–, are examples of different polyatomic ions formed from
nitrogen and oxygen. Other examples are in Table 2 in Section 1.3.
(b) I think this element forms more than one polyatomic ion with oxygen because the nonoxygen element has more than one possible valence.
46. Nitrites can be present in the meat because nitrates react to form nitrites.
47. A Comparison of Elements, Neon, Oxygen, and Magnesium
(a)
(b)
(c)
neon, Ne oxygen, O magnesium, Mg
Number of electrons
10
8
12
Number of valence electrons
8
6
Gains or loses electrons to become stable? neither
gains
loses
Type of ion
none
anion
cation
2
Symbol of ion
none
O
Mg2+
48. (a) A mass spectrometer contains an ion source, an analyzer, and a detector.
(b) In the ion source, a sample is heated and then ionized. The ions are accelerated by an electric
field and then deflected by a magnetic field. The deflection depends on the size of the isotope.
From the ion source, the particles reach a detector, which senses the relative quantities of each
isotope. The analyzer consists of a computer that determines the mass and abundance of each
isotope.
49. Gamma rays have a greater ability to penetrate solid matter than either of the other rays.
Also, gamma rays are high-energy radiation, so they are likely to be most deadly to the cancer
cells.
50. The atomic number of the daughter material will be 2 less than the atomic number of the
parent material. Also, the mass number will be 4 less than that of the parent material. This is
because an alpha particle consists of 2 protons and 2 neutrons, which come from the decay of the
parent material.
51. (a) An atom of any halogen, such as fluorine, could gain the one valence electron from a
sodium atom and become stable.
(b) An atom of any element in Group 16, such as oxygen, could gain the two valence electrons
from a calcium atom and become stable.
52. The current periodic table lists elements according to increasing atomic number, not atomic
mass. Otherwise, the arrangement is very similar.
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53. (a) I would first write the symbol for sulfur, S. Then I would determine how many valence
electrons sulfur has by looking in the periodic table. I know that sulfur has 16 electrons, which
means there are 2 electrons in the first energy level, 8 electrons in the next level, and 6 valence
electrons. I would draw dots to represent the 6 valence electrons around the “S” symbol, starting
at the top and going around clockwise until all 6 dots are placed. So, for sulfur, the Lewis symbol
would consist of the letter S, with 2 dots at the top, 2 dots on the right side, 1 at the bottom, and 1
on the left.
(b) The Bohr–Rutherford diagram shows all electrons, not just valence electrons. The Bohr–
Rutherford diagram also typically shows the number of protons and neutrons in the nucleus.
54. (a) Mendeleev proposed a periodic table upon which the modern periodic table is based. He
ordered elements according to increasing atomic mass and properties. He predicted the presence
and properties of yet-undiscovered elements.
(b) Dobereiner noticed that groups of three elements had similar properties.
(c) Newlands noticed that the properties of elements repeated every seven elements when they
were ordered according to atomic mass.
55. The radius of an individual chlorine atom, Cl, differs from the radius of a chlorine atom in a
chlorine molecule, Cl2, because the atomic radius of an individual chlorine atom is the distance
from the nucleus to the valence electrons. This radius would be a bit longer than the radius of
chlorine in a diatomic molecule, which is half the distance between the two nuclei.
56. (a) In general, atomic radius increases from top to bottom in a group.
(b) Each period, as you look down the periodic table, has one more energy level around the atom
than the period above it. This additional energy level increases its volume. Also, outer electrons
are farther from the nucleus and are less tightly held.
57. (a) In general, ionization energy decreases from top to bottom in a group.
(b) For each period, an energy level is added to the atom, so outer electrons are farther from the
nucleus and are less tightly held. It takes less energy to remove a loosely held electron than to
remove one that is closer to the nucleus and thus more tightly held.
(c) As you move from left to right across a period, ionization energy tends to increase.
(d) As atomic radius decreases, the pull on outer electrons increases and it requires more energy
to remove an electron.
Analysis and Application
58. The knowledge from this experiment was empirical knowledge because it was based on
observations.
59. (a) Thoughts are not matter because they have no mass or volume.
(b) Water is matter because it has both mass and volume.
(c) Air is matter because it has both mass and volume.
(d) Bricks are matter because they have both mass and volume.
(e) Ideas are not matter because they have no mass or volume.
60. Alchemists explored the nature of matter and isolated many elements, which eventually led
to the study of atoms.
61. (a) A magnesium atom contains 2 valence electrons.
(b) A magnesium atom contains the same number of electrons as protons: 12. Two of these
electrons are in its first energy level and 8 are in its second energy level. That leaves 2 in the
third energy level: the valence electrons.
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62. Too much salt can cause a person to have high blood pressure because both sodium and
chloride ions are important for body fluid control. If there are too many ions present, the amount
of fluid increases. Blood volume increases, resulting in increased blood pressure.
63. (a) The first ion formed is Fe2+. This is the ferrous, or iron(II), ion.
(b) The second ion formed is Fe3+. This is the ferric, or iron(III), ion.
64. (a) The -ate ion contains one more oxygen atom than an -ite ion contains.
(b) The perchlorate ion contains one more oxygen atom than the chlorate ion contains.
(c) The periodate ion would contain one more oxygen atom than the iodate ion contains, so it
would be IO4–.
65. (a) A beta particle forms during the radioactive decay of C-14 into N-14.
(b) The mass of the atom did not change (both atoms have a mass of 14), but the identity of the
element did change. Only the emission of a beta particle fits this evidence.
66. (a) The positive plate will repel positively charged alpha particles and the negative plate will
attract them. The negative plate will repel negatively charged beta particles and the positive plate
will attract them. Gamma radiation will be unaffected by the charged plates.
(b) Alpha particles are blocked by materials that beta and gamma radiation pass through. Beta
particles are blocked by materials gamma radiation can pass through.
67. Given: atomic mass and abundance of the four isotopes of chromium
Required: atomic mass of chromium
Analysis:
atomic mass = % abundance of isotope 1 (mass of isotope 1) + % abundance of isotope 2 (mass
of isotope 2) + % abundance of isotope 3 (mass of isotope 3) + % abundance of isotope 4 (mass
of isotope 4)
Solution:
Step 1. Substitute the known values into the equation.
atomic mass = 4.35 % (50 u) + 83.79 % (52 u) + 9.50 % (53 u) + 2.36 % (54 u)
Step 2. Solve the equation.
atomic mass = 52.1 u
Statement: The relative atomic mass of chromium 52.1 u.
68. (a) The isotope K-39 is present in greatest abundance.
(b) The atomic mass is much closer to 39 than it is to 40 or 41.
69. Given: atomic mass and abundance of the two isotopes of boron
Required: atomic mass of chromium
Analysis:
atomic mass = % abundance of isotope 1 (mass of isotope 1) + % abundance of isotope 2 (mass
of isotope 2)
Solution:
Step 1. Determine the abundance of B-11.
abundance of B-11 = 100.0 % – 19.8 %
abundance of B-11 = 80.2 %.
Step 2. Substitute the known values into the equation.
atomic mass = 19.8 % (10 u) + 80.2 % (11 u)
Step 3. Solve the equation.
atomic mass = 10.8 u
Statement: The relative atomic mass of boron is 10.8 u.
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70. (a) Fluorine is a representative element and cobalt is not.
(b) Fluorine most closely follows the periodic law.
71. Noble gases were likely discovered so late because they do not readily react with other
elements, and some of them do not react at all. Thus, they were not present in compounds. In
addition, they were all gases and could not be seen.
72. (a) Julius Lothar Meyer proposed a periodic table based on the valence of elements.
(b) The problem with a periodic table based on valence is that some elements have multiple
valences.
73. (a) The two elements are in the same period of the periodic table. I therefore conclude that
the two elements have the same number of energy levels. However, silver contains 10 more
protons than rubidium does, so the effective nuclear charge is higher in silver. The electrons in
silver are more tightly bound to the nucleus than they are in rubidium. The electrons in silver
therefore stay closer to the nucleus, giving silver atoms a smaller radius than rubidium atoms.
(b) Rubidium, silver, and iodine are all in the same period and all have the same number of
valence levels. However, iodine contains even more protons than silver does, so the electrons in
iodine are more closely bound to the nucleus than they are in either rubidium or silver.
Therefore, iodine is even smaller than silver.
74. I think that the second ionization energy is greater than the first ionization energy because the
first electron removed from a magnesium atom is removed from a neutral atom, leaving an ion
with a +1 valence. The effective nuclear charge is now greater on the remaining electrons, so
more energy is required to remove it from the positively charged ion.
Evaluation
75. If the International Union of Pure and Applied Chemistry (IUPAC) had not been established,
the symbols of elements would differ in different countries, as would units of measurement.
There would probably be more misunderstandings between chemists working in different
countries and new discoveries would not be communicated as well.
76. (a) Bohr's work led to a model of the atom in which electrons exist in definite energy levels.
(b) Rutherford's work showed that most of the atom is empty space, and it contains a dense,
positively charged nucleus.
(c) The Bohr–Rutherford model of the atom shows electrons in fixed energy levels surrounding a
dense, positively charged nucleus.
77. (a) The first part of the calculation was correct: finding the percentage of the remaining
isotope. However, the following calculation is not an appropriate method of determining the
atomic mass. It does not take into account the relative quantities of the various isotopes.
(b) Given: atomic mass and abundance of the three isotopes of an element
Required: atomic mass of element
Analysis:
atomic mass = % abundance of isotope 1 (mass of isotope 1) + % abundance of isotope 2 (mass
of isotope 2) + % abundance of isotope 3 (mass of isotope 3)
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Solution:
Step 1. Determine the abundance of element.
abundance of element = 100.0 % – (48.2 % + 32.1 %)
abundance of element = 19.7 %
Step 2. Substitute the known values into the equation.
atomic mass = 48.2 % (107 u) + 32.1 % (105 u) + 19.7 % (106 u)
Step 3. Solve the equation.
atomic mass = 106 u
Statement: The relative atomic mass of the element is 106 u.
(c) The best procedure is the one that considers the percentages of the isotopes, as this more
accurately reflects how much there is of each isotope.
78. The arrangement of elements on a periodic table resembles a theory because information on
the table might change as more knowledge becomes available. Also, it is an explanation for
observations.
79. (a) The radius of a calcium ion is smaller than the radius of a calcium atom because the outer
energy level of the atom was lost when the atom lost 2 electrons and formed an ion.
(b) The radius of a sulfide ion is larger than the radius of a sulfur atom. Although the electrons
the atom gained during ionization were added to the existing valence level, the repulsion among
the electrons increases so the electrons spread out more.
80. (a) Larger atomic radius: Be; larger ionic radius: N; larger ionization energy: N; larger
electron affinity: N.
(b) Larger atomic radius: As; larger ionic radius: As; larger ionization energy: N; larger electron
affinity: N.
Reflect on Your Learning
81. The main difference between theories and laws is that laws have been accepted after being
extensively tested and observed. They are based on observations. We assume that laws will not
change. Theories, however, are scientists’ best explanations for observations. Theories tend to
change as more evidence becomes available and different explanations are needed.
82. Answers may vary. Sample answer: My current concept of education is similar to the
development of the atomic theory because my concept of education changed as I learned more
about it. For example, in Grade 1, I might have considered education to be learning to share and
learning to read. I now consider education to be much broader; I am learning many things
besides the facts taught in classes. My education has a purpose: it will help me to learn
continuously and to get a job. Just as my understanding of education changed as I collected
information, so our model of the atom has changed as more technologies became available and
provided further evidence.
83. (a) The nitrate ion, NO3–, is both a polyatomic ion and an anion.
(b) The ammonium ion, NH4+, is both a polyatomic ion and a cation.
(c) The iron(II) ion is the ferrous ion, Fe2+.
(d) The tin(IV) ion is the stannic ion, Sn4+.
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84. (a) Not everyone needs to be concerned about radon in the home. If you live in an area where
little radon is produced in the bedrock, or if your home does not have a basement, you are in less
danger from radon.
(b) Answers may vary. Sample answer: Yes, I checked my home for radon using a radon-testing
kit.
(c) If remediation has taken place, it would be either keeping radon from entering or increasing
ventilation.
85. (a) The best metals for use in my construction project would be transition metals.
(b) Transition metals are strong, conduct electric current well, and some are unreactive in water.
86. Element 115 is temporarily named ununpentium.
87. (a) This situation is analogous to removing a valence electron from an atom because energy
must be exerted to remove both the puck from the hands and the electron from the atom.
(b) The term applied to the amount of energy needed to remove a valence electron from an atom
is ionization energy.
Research
88. (a) The hardness of diamonds makes them suitable for cutting and grinding of other
materials. Their clarity and beauty make them desirable for jewellery.
(b) Cost was the determining factor in the widespread use of charcoal in ore extraction: it was
cheap. The vast forests in Canada made wood readily available to make charcoal.
(c) Quebec is the commercial producer of graphite in Canada.
89. (a) The deposit of fullerenes is located in the Sudbury Meteorite Crater in Ontario.
(b) Cami found buckminsterfullerene in space: in a star 6.5 million light years from Earth.
90. (a) A quark is a small, subatomic particle that makes up other subatomic particles, such as
protons and neutrons.
(b) The flavours are up, down, charm, strange, top, and bottom.
(c) Quarks are elemental subatomic particles, as are electrons. Quarks make up neutrons and
protons.
91. (a) Although there are exceptions, compounds containing the cyanide ion are highly toxic to
humans and other organisms.
(b) Although chromium in other forms is safe, chromium in the chromate ion is both toxic and
carcinogenic.
92. (a) The maximum concentration of radon considered to be safe is 200 Bq/m3.
(b) Radon emits alpha particles.
(c) The quantity of radon entering a building can be reduced by sealing any openings through
which radon can enter. Increasing ventilation and filtering the air can reduce the concentration of
radon present.
93. (a) Henry Moseley proposed changing the periodic table to order the elements by atomic
number instead of increasing atomic mass.
(b) On a table based on atomic mass, cobalt and nickel were reversed, as were argon and
potassium, and tellurium and iodine.
(c) Scientists suspected that the change from atomic mass to atomic number needed to be made
because the properties of these elements did not match the properties of the other elements in the
same group. Properties were more similar when the order of elements on the table was according
to atomic number.
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