Unit 1: Matter, Chemical Trends, and Chemical Bonding
Chapter 1: Atomic Structure and the Periodical Table
Section 1.1: The Nature of Chemistry, pages 2–3
1. Matter is any substance that has mass and space.
2. Table 1 What Chemists Do
What chemists
Macroscopic or
Type of knowledge
do
microscopic
gained
Where it occurs: in the lab or on
paper
experiment
macroscopic
empirical
lab
conceptualize
microscopic
theoretical
on paper
measure
macroscopic
empirical
lab
imagine
microscopic
theoretical
on paper
theorize
microscopic
theoretical
on paper
observe
macroscopic
empirical
lab
3. a
4. Table 2 Matter
Is it matter?
Item
(yes/no)
wood
yes
air
yes
sleep
gravity
no
no
How do you know?
It has mass and takes up space.
Air has mass and takes up space. For example, a tire that is filled with air
weighs more than a flat tire.
Sleep has no mass of its own and it does not take up space.
Gravity is not matter; it is a force. Gravity gives matter weight (not mass),
but it does not have weight of its own.
5.
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Chapter 1: Atomic Structure and the Periodic Table 1-1
6. Table 3 Objects
Observation
The object travels very slowly in a
straight line.
Theory
The object is round with a soft, fuzzy exterior.
The object travels very fast in a
straight line.
The object is round with a hard, smooth
exterior.
The object travels smoothly, but it
does not travel in a straight line.
The object has a rounded shape but it is not
round. It is some kind of three-dimensional
oval.
The object slides rather than rolls.
The object is not rounded at all. Instead, it has
flat faces.
The object is somewhat rounded, but it has a
very bumpy, irregular surface.
The object travels in an erratic path
and bounces up and down as it
travels.
Sketch
Section 1.2: Atomic Structure, pages 4–6
1. The philosopher’s stone could turn common metals into gold.
2. Figure 1
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Chapter 1: Atomic Structure and the Periodic Table 1-2
3. (a) When Rutherford fired positive alpha particles at a thin sheet of gold foil, he expected that the particles
would pass through the foil without changing their path.
(b) To make this assumption, Rutherford was using the plum pudding model, in which negative electrons (the
fruit) were embedded evenly within a uniformly charged sphere that was positive in charge.
(c) The result Rutherford got in his experiment was that a few of the alpha particles were deflected at large
angles. This surprised Rutherford because he had predicted that all of the particles would pass straight through
the foil without changing their path.
(d) This result led Rutherford to conclude that most of the mass of the gold atoms was concentrated in very
small cores that occasionally were hit by the streaming particles. He called these cores “nuclei” and changed
his model of the atom to one in which most of the atom’s mass is concentrated in a small, dense, positively
charged nucleus.
4. (a) Given: approximate mass of an electron, me = 9.11 ! 10 –31 kg
–
approximate mass of a proton, mp = 1.67 ! 10
–27
kg
+
Required: comparison and ratio of mass of a proton and mass of an electron
Analysis: Compare mp and me , and then calculate mp / me .
+
Solution: 1.67 ! 10
mp+
me –
mp+
me –
!
–27
+
–
kg > 9.11 ! 10
mp+ > me –
–31
–
kg
1.67 ! 10 –27 kg
9.11 ! 10 –31 kg
! 1830
Statement: A proton is greater in mass than an electron. The mass of a proton is approximately 1830 times the
mass of an electron.
(b) Given: approximate mass of an electron, me = 9.11 ! 10 –31 kg
–
approximate mass of a proton or neutron, mp = mn = 1.67 ! 10 –27 kg
+
0
Required: ratio of mass of an alpha particle and mass of an electron
Analysis: An alpha particle, ! , is composed of 2 protons and 2 neutrons. Calculate m! / me .
Solution:
m!
me –
m!
me –
!
(
4 1.67 " 10
9.11 " 10
–27
–31
kg
–
)
kg
! 7330
Statement: The mass of an alpha particle is approximately 7330 times the mass of an electron.
(c) My answer to part (b) supports Rutherford’s original expectation for the gold foil experiment because the
alpha particles were travelling at a high speed and their mass was more than 7000 times greater than the mass
of an electron. Therefore, you would expect the relatively tiny electrons not to deflect the alpha particles very
much.
(d) My answer to part (b) supports the conclusion Rutherford drew from the gold foil experiment about the
nucleus of an atom because Rutherford concluded that the alpha particles must have occasionally run into
particles that were comparable in size and mass to themselves. He identified these large particles as the nuclei
of the gold atoms.
5. (a) 148 Xx has 8 protons, 8 electrons, and 6 neutrons.
(b)
31
16
(c)
63
45
Gx has 16 protons, 16 electrons, and 15 neutrons.
Rp has 45 protons, 45 electrons, and 18 neutrons.
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Chapter 1: Atomic Structure and the Periodic Table 1-3
6. (a) Two possible configurations for a hypothetical element with mass number 14 are
10 protons, 4 neutrons, and 10 electrons and
(b) A model of
14
7
14
7
14
4
X and
14
7
X.
14
4
X has
X has 7 protons, 7 neutrons, and 7 electrons.
X from part (a).
Section 1.3: Ions and the Octet Rule, pages 7–9
1. Among the first 18 elements, the most stable configuration for an atom is to have its outermost electron shell
contain either 2 electrons or 8 electrons.
2. d
3. False. All of the noble gases among the first 18 elements except helium are stable because they have 8
electrons in their valence shell.
4. (a) (i)
(ii)
(iii)
(b) Of the elements drawn in part (a), argon is the most stable because it has a full octet, 8 electrons, in its
outer valence shell.
(c) Phosphorus is likely to gain electrons to become more stable. It is likely to gain 3 electrons, because that is
the number required to fill its outer valence shell so that it has 8 electrons.
(d) Sodium is likely to lose electrons to become more stable. It is likely to lose 1 electron to give it a full outer
valence shell of 8 electrons.
5. (a), (b)
Table 1 Magnesium Atom
# of protons
12
# of neutrons
12
# of electrons 12
Table 2 Magnesium Ion
# of protons
12
# of neutrons
12
# of electrons 10
charge
0
charge
+2
(c) Mg takes a +2 charge when it ionizes.
(d) After Mg ionizes, its outer valence shell is an octet, the most stable configuration. The Mg2+ ion resembles
the noble gas neon.
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Chapter 1: Atomic Structure and the Periodic Table 1-4
6. (a)
Table 3 Sulfur Atom
Table 4 Sulfur Ion
# of protons
16
# of protons
16
# of neutrons
16
# of neutrons
16
# of electrons 16
# of electrons
18
charge
0
charge
–2
(b) sulfide
(c) Sulfur is more stable after it ionizes because its outer valence shell becomes an octet, the most stable
configuration. The S2– ion resembles the noble gas argon.
7. (a) The classical name for Cu2+ is cupric; the IUPAC name is copper(II).
(b) The name for Cl– is chloride.
(c) The classical name for Pb2+ is plumbous; the IUPAC name is lead(II).
(d) The name for SO32– is sulfite.
8. A compound of tin, Sn, and fluoride, F, is used in toothpastes. One tin ion combines with two Cl– ions. The
name of this compound is stannous fluoride.
9. A compound of iron, Fe, and oxygen, O, forms rust. Two iron ions combine with three O2– ions. The name
of this compound is ferric oxide.
Section 1.4: Isotopes, Radioisotopes, and Atomic Mass, pages 10–12
1. Two different isotopes of an element have the same number of protons but different numbers of neutrons.
2. True
3. (a) Diagram (iv) represents the same element as diagram (i) because both atoms have the same number of
electrons, 6.
(b) Diagram (iii) represents the same element as diagram (ii) because both atoms have the same number of
electrons, 7.
(c) Diagram (i) represents carbon-12.
(d) Diagram (ii) represents nitrogen-14.
(e) Diagram (iii) represents nitrogen-15.
(f) Diagram (iv) represents carbon-14.
4. (a)
(b) The diagram for O-16 represents the most abundant oxygen isotope in nature because the atomic mass of
O-16 is 16 u, which is the same as the atomic mass of oxygen, 16.00 u.
(c) I would expect O-18 to be very uncommon in nature because the atomic mass of oxygen is not at all close
to 18 u.
5. (a) Ion path 3 identifies the lightest isotope of boron; path 1 identifies the heaviest isotope. You know this
because the lightest isotope of boron will be deflected most by the magnetic field, while the heaviest isotope
will be deflected least.
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Chapter 1: Atomic Structure and the Periodic Table 1-5
(b) Table 1 Boron Isotopes
Boron isotope
Path
Protons
Neutrons
B-10
path 3
5
5
B-11
path 2
5
6
B-12
path 1
5
7
6. The radiation consists of beta particles. All three types of radiation—alpha, beta, and gamma—are stopped
by lead. Only beta and alpha are charged particles. Beta particles are larger in mass than a hydrogen atom of
atomic mass 1, so the radiation must be beta.
7. A substance that is a radioisotope would be unstable, meaning that it would break down spontaneously over
time. The substance would also emit some kind of radiation upon breakdown. This might be alpha particles,
beta particles, or gamma rays.
8. Given: isotopic abundances of five zinc isotopes: Zn-64, 48.6 %; Zn-66, 27.9 %; Zn-67, 4.1 %;
Zn-68, 18.8 %; Zn-70, 0.6 %
Required: atomic mass of zinc
Analysis: atomic mass = % abundance of isotope 1 (mass of isotope 1) +
% abundance of isotope 2 (mass of isotope 2) + ...
Solution: atomic mass = 48.6 % (64 u) + 27.9 % (66 u) + 4.1 % (67 u) + 18.8 % (68 u) + 0.6 % (70 u)
= 31.10 u + 18.41 u + 2.747 u + 12.78 u + 0.42 u (extra digits carried)
= 65.5 u
Statement: The atomic mass of zinc is 65.5 u.
Section 1.5: The Periodic Table and Periodic Law, pages 13–14
1. Vertical columns called groups feature atoms that all share the same number of valence electrons.
2. False. All elements within a group or column of the periodic table share similar properties of reactivity.
3. a
4. Table 1 Properties of Elements
Metal or
State at room
Group
Location
Reactivity non-metal?
Reacts with
temperature
halogens
Group 17, 2nd
high
non-metal
solid, liquid,
metals,
column from right
or gas
hydrogen
alkali metals
Group 1, 1st column
high
metal
solid
halogens, water,
on left (excluding H)
air
noble gases
Group 18, far right
none
non-metal
gas
no reactions
column
transition
Groups 3–13, row 4
moderate metal
solid
oxygen, acids
metals
and below
alkaline earth
Group 2, 2nd column high
metal
solid
oxygen,
metals
on left
hydrogen, water
5. The patterns within a typical period in the periodic table are as follows: The period starts on the left with a
highly reactive alkali metal. This is followed by an alkaline earth metal, and then, in Period 4 and below, a
series of transitional metals. At (or near) Groups 14 and 15 you see metalloids, followed by a highly reactive
non-metal, then a halogen, and then a noble gas. The same pattern repeats throughout the periodic table.
6. (a) Within a group, the valence of atoms does not change.
(b) Within a period, the valence of atoms starts at 1 valence electron at the left end of the period and increases
as you move to the right, ending with a full octet, or 8 valence electrons, at the right end of the table.
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Chapter 1: Atomic Structure and the Periodic Table 1-6
7. Table 2 Lewis Diagram Reactivity Prediction
Element Explanation
P
P needs 3 electrons to fill its valence shell, so you would expect it, for
example, to react with 3 atoms that each give up 1 electron.
Kr
Kr has a full valence shell, so it will be inert, or non-reactive.
Li
Li has only 1 electron in its valence shell, so you would expect it to give up
its electron and react with other atoms that need to pick up electrons.
Lewis diagram
Al
Al has only 3 electrons in its valence shell, so you would expect it to give
up those electrons and react with other atoms that need to pick up
electrons.
8. Element X is calcium. As a representative element, element X must be in one of Groups 1, 2, or 13–18.
Element X is bordered on one side by a transition metal. The transition metals run from Group 3 through 11, so
no element from Groups 13–18 could be element X. Element X does not react strongly with water, so it could
not be an alkali metal (Group 1). It must be a Group 2 element. It cannot be beryllium or magnesium, as they
are not bordered by a transition metal, and it is not strontium, so element X must be calcium.
Section 1.6: Chemistry Journal: A Not-So-Elementary Task, page 15
1. The first scientist to discover a repeating pattern among the elements was John Newlands.
2. False. Before Hennig Brand discovered phosphorous in urine, only a few elements were known.
3. c
4. Table 1 Development of the Periodic Table
Scientist
Date
Scheme
Strength
Flaw
Brand
1649
isolated first element
began search for elements no pattern found
Lavoisier
1789
listed elements
identified 33 elements
no pattern found
Dobereiner
1800s triads of 3 elements
first to show trend
limited pattern
Newlands
1649
law of octaves
regular pattern, true
worked only for first
periodicity
20 elements
Mendeleev
1869
table of elements
comprehensive pattern; later elements left out
left holes for unknowns
Lothar Meyer 1864
table of elements
real pattern
organized by valence
Moseley
1900s added to Mendeleev’s found missing elements
some elements still
scheme
unknown
Seaborg
1940s 10 new elements
completed periodic
still may be unknown
table
elements
5. For all of the first 18 elements except for hydrogen, when you subtract the atomic number of the element
from the atomic number of the element below it, the difference is 8. This pattern does not continue on lower
rows of the table. Once you reach the transition metals, the difference of 8 does not continue.
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Chapter 1: Atomic Structure and the Periodic Table 1-7
Section 1.7: Periodic Trends in Atomic Properties, pages 16–18
1. b
2. c
3. In a diatomic oxygen molecule, the atomic radius is defined as half the distance between the centres of the
nuclei of the two oxygen atoms.
4. (a) Between oxygen and nitrogen, oxygen has the greater effective nuclear charge because it has more
protons, but its outer electrons are all within the same energy level as in nitrogen. Therefore, the attraction
between oxygen’s electrons and its nucleus is stronger than that of nitrogen and its electrons.
(b) Since oxygen has the greater effective nuclear charge, it holds onto its electrons more tightly, meaning
oxygen has a smaller atomic radius than nitrogen.
(c) Between oxygen and sulfur, oxygen has the greater effective nuclear charge because although it has fewer
protons, the electrons in sulfur’s valence shell are at a higher energy level than the electrons in oxygen’s
valence shell. This means that sulfur’s outer electrons are effectively shielded from attraction, so they are less
strongly held than oxygen’s outer electrons.
(d) Since oxygen has a greater effective nuclear charge than sulfur, it has a smaller atomic radius than sulfur.
5. (a)
(b) In the Na atom, each electron is pulled by
(c) In the Na ion, each electron is pulled by
(d) Since
1
of the total nuclear attraction force.
11
1
of the total nuclear attraction force.
10
1
1
is less than
, the force of attraction exerted by the nucleus on each electron in the sodium ion
11
10
is greater than in the sodium atom. This means that the sodium atom will have a weaker hold on its electrons
than the sodium ion does, resulting in the atom being larger in size than the ion.
6. (a)
(b) In the Cl atom, each electron is pulled by
1
of the total nuclear attraction force. In the Cl– ion, each
17
1
of the total attraction force.
18
1
1
(c) Since
is greater than
, the force of attraction exerted by the nucleus on each electron in the chlorine
17
18
electron is pulled by
atom is greater than in the chloride ion. This means that the chlorine atom has a stronger hold on its electrons
than the chloride ion does, resulting in the atom being smaller than the ion. Chlorine has a stronger hold on its
electrons than sodium does.
7. When a chlorine atom gets ionized, energy is released.
8. a
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Chapter 1: Atomic Structure and the Periodic Table 1-8
Chapter 1 Questions, pages 20–21
1. (a) empirical
(b) empirical
(c) theoretical
(d) theoretical
2. b
3. False. The “holes” in Mendeleev’s periodic table proved that some elements were still undiscovered.
4. (a) The mass of a lithium atom is 7 u.
(b) Given: 1 u = 1.660 540 2 ! 10 –27 kg
Required: mass of a lithium atom in kg
Analysis: Use mLi = 7 u .
Solution: mLi = 7(1.660 540 2 ! 10 –27 kg)
= 1.162 378 1 !10 –26 kg
Statement: The mass of a lithium atom is approximately 1.162 ! 10 –26 kg .
5. Table 1 Ions and Atoms
Proton
Neutron
atom
number of protons
number of neutrons varies;
matches atomic number equals mass number minus
atomic number
negative number of protons
number of neutrons varies;
ion
matches atomic number equals mass number minus
atomic number
positive
ion
number of protons
matches atomic number
number of neutrons varies;
equals mass number minus
atomic number
Electron
number of electrons matches
atomic number
number of electrons is greater
than atomic number; equals
atomic number minus the
charge
number of electrons is less than
atomic number; equals atomic
number minus the charge
6. (a)
(b) Table 2 Potassium Atom
Table 3 Potassium Ion
# of protons
19
# of protons
19
# of neutrons
20
# of neutrons
20
# of electrons 19
# of electrons
18
charge
0
charge
+1
7. (a) Since calcium has an atomic mass of 40.078 u with 20 protons and 20 electrons, the most common
calcium isotope is likely to be C-20, with 20 protons, 20 neutrons, and 20 electrons.
(b) Another calcium isotope you might find would have 20 protons, 21 neutrons, and 20 electrons. This isotope
is likely to be scarce. Its atomic mass raises calcium’s atomic mass to only slightly above 40 u.
8. The element is arsenic.
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Chapter 1: Atomic Structure and the Periodic Table 1-9
9. (a) Table 4 Bromine and Potassium Comparison
Bromine (Br)
number of protons
35
atomic radius
small
ionic radius
large
Potassium (K)
19
large
small
electron affinity
high
low
number of valence electrons
7 (maximum for non-noble gas)
1
screening of the nucleus
same
same
first ionization energy
high
low
(b) Both atoms have the same amount of screening since their electrons exist in the same energy level. Since
Br has 16 more protons than K, its attraction to its electrons is much greater, so it has a greater electron
affinity, and a much higher first ionization energy than K.
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Chapter 1: Atomic Structure and the Periodic Table 1-10