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GENERAL CHEMISTRY
Principles and Modern Applications
PETRUCCI
HERRING
MADURA
Atoms and the
Atomic Theory
TENTH EDITION
BISSONNETTE
2
PHILIP DUTTON
UNIVERSITY OF WINDSOR
DEPARTMENT OF CHEMISTRY AND
BIOCHEMISTRY
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General Chemistry: Chapter 2
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Atoms and the
Atomic Theory
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CONTENTS
2-1
Early Chemical Discoveries and
the Atomic Theory
2-2
Electrons and Other Discoveries
in Atomic Physics
2-3
The Nuclear Atom
2-4
Chemical Elements
2-5
Atomic Mass
2-6
Introduction to the Periodic Table
2-7
The Concept of the Mole and the
Avogadro Constant
2-8
Using the Mole Concept in
Calculations
General Chemistry: Chapter 2
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2-1 Early Discoveries and the Atomic Theory
Lavoisier 1774
Law of conservation of mass
Proust 1799
Law of constant composition
Dalton 1803-1888
Atomic Theory
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General Chemistry: Chapter 2
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2-4
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AgNO3
FIGURE 2-2
K2CrO4
Ag2CrO4
Mass is conserved during a chemical reaction
Total mass of substance is constant before and after reaction
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General Chemistry: Chapter 2
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2-6
Law of constant composition:
• All sample of a compound has same
composition- same proportion in masses
of its constituents.
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2-7
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2-8
Dalton’s Atomic Theory
1. Each element is composed of small particles
called atoms. Atoms are neither created
nor destroyed in chemical reactions.
2. All atoms of a given element are identical
and differ from all other elements
3. Compounds are formed when atoms of
more than one element combine in simple
numerical ratios.
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General Chemistry: Chapter 2
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If two elements form more than a single compound, the masses of one
element combined with a fixed mass of the second are in the ratio of
small whole numbers.
Law of multiple proportions:
• In forming carbon
monoxide, 1.0 g of carbon
combines with 1.33 g of
oxygen.
•
In forming carbon dioxide,
1.0 g of carbon combines
with 2.66 g of oxygen.
Figure 2-3
Consequences of Dalton’s theory
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General Chemistry: Chapter 2
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2-2
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Electrons and Other Discoveries
in Atomic Physics
General Chemistry: Chapter 2
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FIGURE 2-5
Effect of a magnetic field on charged particles
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General Chemistry: Chapter 2
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FIGURE 2-6
Cathode ray tube
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General Chemistry: Chapter 2
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FIGURE 2-7
In 1897 Thomson -Electron m/e = -5.6857 × 10-9 g coulomb-1
Thomson concluded that CRs are negatively charged
fundamental particles of matter found in all atoms.
Cathode rays and their properties
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General Chemistry: Chapter 2
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Figure 2-8
 From 1906-1914 Robert Millikan showed ionized oil drops can
be balanced against the pull of gravity by an electric field.
The charge is an integral multiple of the electronic charge, e.
Speculations about how the charged particles incorporated
atoms result atom models
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Millikan’s oil-drop experiment
General Chemistry: Chapter 2
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Thomson Model
Neutral atom
Ions carry net charge
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2 - 16
X-Rays and Radioactivity
Radioactivity is the spontaneous emission
of radiation from a substance.
• X-rays and g-rays are high-energy light.
• a-particles are a stream of helium nuclei,
He2+.
• b-particles are a stream of high speed
electrons that originate in the nucleus.
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General Chemistry: Chapter 2
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2 - 18
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2-3 The Nuclear Atom
Geiger and Rutherford
1909
Figure 2-11
The scattering of  particles by metal foil
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General Chemistry: Chapter 2
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• Most of the mass and all of the positive
charge is concentrated in a small region
called the nucleus .
• There are as many electrons outside the
nucleus as there are units of positive
charge on the nucleus
Figure 2-12
The  -particle experiment
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General Chemistry: Chapter 2
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Rutherford Model:
• Most of the mass and all of the positive charge of an atom
centered in very small region called nucleus the rest is just
empty space
• The magnitude of positive charge differ from atom to atom and
the mass is half of the atomic weight of element
• There are same amount of electrons, equally number of nucleus
charge, occupy the outside of the nucleus. The atom as a whole
is electrically neutral.
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General Chemistry: Chapter 2
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Rutherford
protons 1919
James Chadwick
neutrons 1932
Figure 2-13
The nuclear atom – illustrated by the helium atom
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General Chemistry: Chapter 2
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Slide 23 of 27
General Chemistry: Chapter 2
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Scale of Atoms
The heaviest atom has a mass of only 4.8 x 10-22 g
and a diameter of only 5 x 10-10 m.
Useful units:
• 1 amu (atomic mass unit) = 1.66054 x 10-24 kg
• 1 pm (picometer) = 1 x 10-12 m
• 1 Å (Angstrom) = 1 x 10-10 m = 100 pm = 1 x 10-8 cm
Biggest atom is 240 amu and is 50 Å across.
Typical C-C bond length 154 pm (1.54 Å)
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General Chemistry: Chapter 2
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2-4 Chemical Elements
To represent a particular atom we use symbolism:
A= mass number
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Z = atomic number
General Chemistry: Chapter 2
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isotopes:
Atoms have same atomic number but different
mass number called isotopes.
Ne Z=10 but A=20, 21, 22
Natural Abundance?
Ions?
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General Chemistry: Chapter 2
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2-5 Atomic Mass
Weighted Average
Atomic Mass of an Element
Equation (2.3)
fractional
atomic
fractional
atomic
abundance x mass of + abundance x mass of + ……
of isotope 1 isotope 1 of isotope 2 isotope 2
=
Aave
=
where
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x1 x
A1
+
x2 x A2
+ …… xn x An
x1 + x2+ + xn = 1.0
General Chemistry: Chapter 2
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Atomic Mass Unit(amu)
• Mass of 1/12 of 1 12C isotope is called
1amu
• Mass of all atoms are given with respect to
12C isotope.
• All mass number are not whole number
except C-12 isotope.
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General Chemistry: Chapter 2
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2 - 29
Determine Atomic Mass of Isotopes
Figure 2-14
A mass spectrometer and a mass spectrum
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General Chemistry: Chapter 2
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The Periodic Table
Read atomic masses.
Read the ions formed by main group elements.
Read the electron configuration.
Learn trends in physical and chemical properties.
We will discuss these in detail in Chapter 9.
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General Chemistry: Chapter 2
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Alkali Metals
The Periodic table
Alkaline Earths
Halogens
Noble Gases
Main Group
Transition Metals
Main Group
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Lanthanides and Actinides
General Chemistry: Chapter 2
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2-7
The Concept of the Mole and the
Avogadro Constant
Physically counting atoms is impossible.
We must be able to relate measured mass to
numbers of atoms.
buying nails by the pound or kilogram.
using atoms by the gram
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General Chemistry: Chapter 2
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Avogadro constant, NA
• The mole is an amount of substance that
contains the same number of elementary
entities as there are carbon-12 atoms in
exactly 12 g of carbon-12.
NA = 6.02214179 x 1023 mol-1
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General Chemistry: Chapter 2
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Figure 2-17
One mole of an element
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General Chemistry: Chapter 2
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2 - 37
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2 - 38
General Chemistry
Principles & Modern Applications
10th Edition
Petrucci/Herring/Madura/Bissonnette
Chapter 2
Atoms and the Atomic Theory
Dr. Wendy Pell
University of Ottawa
Copyright © 2011 Pearson Canada Inc.
When a match burns its mass increases.
True or False, the only conclusion to be
drawn here is that the Law of Conservation
of Mass is incorrect?
1. True
2. False
3. Not sure?
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Slide 40 of 23
When a match burns its mass increases.
True or False, the only conclusion to be
drawn here is that the Law of Conservation
of Mass is incorrect?
1. True
2. False
3. Not sure?
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Slide 41 of 23
After 10 gram sample of lithium
metal is reacted in a closed
container with 44.32 g of chlorine
gas; 1.32 g of lithium remain, the
chlorine is consumed completely.
What mass of lithium chloride is
formed ?
1. 54.32 g
2. 8.68 g
3. 53.00 g
4. 55.64 g
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Slide 42 of 23
After 10 gram sample of lithium
metal is reacted in a closed
container with 44.32 g of chlorine
gas; 1.32 g of lithium remain, the
chlorine is consumed completely.
What mass of lithium chloride is
formed ?
1. 54.32 g
2. 8.68 g
3. 53.00 g
4. 55.64 g
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Slide 43 of 23
Given the diagram of a to the right,
which of the following diagrams are
incorrect?
+
1.
+
-
N
-
+
-
2.
N S
-
-
+
S
+
3. Both 1 and 2 are incorrect
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Slide 44 of 23
which of the following diagrams are
incorrect?
+
1.
-
2.
N S
-
+
-
N
-
+
S
+
3. Both 1 and 2 are incorrect
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Slide 45 of 23
Which of the following statements is
incorrect using only the periodic table
to the right.
1. Argon is the heaviest atom.
2. The heaviest element in group
one is also the lightest element in
period 3.
3. The lightest gaseous element is He.
4. The heaviest gaseous element is Cl2.
5. The heaviest element in group 18 is also the heaviest element in period 1.
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Slide 46 of 23
Which of the following statements is
incorrect using only the periodic table
to the right.
1. Argon is the heaviest atom.
2. The heaviest element in group
one is also the lightest element in
period 3.
3. The lightest gaseous element is He.
4. The heaviest gaseous element is Cl2.
5. The heaviest element in group 18 is also the heaviest element in period 1.
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Slide 47 of 23
To the right is a portion of the
periodic table. Which of the following
statements is correct?
1. Mg2+, Al+ and Si all have the
same number of electrons.
2. H and He2+ have the same mass.
3. Li+, Be2+ and B3+ all have the same number of electrons.
4. Li+, Be2+ and B3+ all have the same number of protons.
5. H, Li and Na all have the same number of electrons.
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Slide 48 of 23
To the right is a portion of the
periodic table. Which of the following
statements is correct?
1. Mg2+, Al+ and Si all have the
same number of electrons.
2. H and He2+ have the same mass.
3. Li+, Be2+ and B3+ all have the same number of electrons.
4. Li+, Be2+ and B3+ all have the same number of protons.
5. H, Li and Na all have the same number of electrons.
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Slide 49 of 23
Bromine has two naturally occurring isotopes, bromine-79 and
bromine-81. Bromine exists as a diatomic compound, ie. Br2.
How many different Br2 molecules are possible and what are
their masses?
1. 2 different molecules: 158 and 162 u.
2. 3 different molecules: 158, 160, and 162 u.
3. 3 different molecules: 158, 159, and 160 u.
4. 4 different molecules: 158, 159, 160 and 161 u.
5. 4 different molecules: 158, 160, 161, and 162 u.
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Slide 50 of 23
Bromine has two naturally occurring isotopes, bromine-79 and
bromine-81. Bromine exists as a diatomic compound, ie. Br2.
How many different Br2 molecules are possible and what are
their masses?
1. 2 different molecules: 158 and 162 u.
2. 3 different molecules: 158, 160, and 162 u.
3. 3 different molecules: 158, 159, and 160 u.
4. 4 different molecules: 158, 159, 160 and 161 u.
5. 4 different molecules: 158, 160, 161, and 162 u.
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Slide 51 of 23
Given the diagram below, which of the following statements is
incorrect?
1. The ion marked A
corresponds to m/z
204.
2. The ion marked A is
lighter than the ion
marked B.
3. The ion marked B
corresponds to m/z 198.
4. The ion marked A is the
lightest isotope of Hg.
B
A
Given the diagram below, which of the following statements is incorrect?
1. The ion marked A
corresponds to m/z 204.
2. The ion marked A is lighter
than the ion marked B.
B
A
3. The ion marked B
corresponds to m/z 198.
4. The ion marked A is the
lightest isotope of Hg.
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Slide 53 of 23
Without doing detailed calculations and using the periodic table to the
right, which of the following contains the greatest number of atoms?
1. 1.0 kg of hydrogen gas (ie. H2).
2. 1.0 kg of helium gas (ie. He).
3. 1.0 kg of water vapor (ie. H2O).
4. 1.0 kg of liquid water (ie. H2O).
5. 1.0 kg of nitrogen (ie. N2).
6. 1 kg of Aluminium metal (i.e Al)
Without doing detailed
calculations and using the
periodic table to the right, which
of the following contains the
greatest number of atoms?
1. 1.0 kg of hydrogen gas (ie. H2).
2. 1.0 kg of helium gas (ie. He).
3. 1.0 kg of water vapor (ie. H2O).
4. 1.0 kg of liquid water (ie. H2O).
5. 1.0 kg of nitrogen (ie. N2).
Without doing detailed calculations
and using the periodic table to the
right, which of the following samples
contain the least number of atoms?
1. 1.0 g of oxygen gas (ie. O2).
2. 1.0 g of sulphur (ie. S8).
3. 1.0 g of water vapor (ie. H2O).
4. 1.0 g of liquid water (ie. H2O).
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Slide 56 of 23
Without doing detailed calculations
and using the periodic table to the
right, which of the following samples
contain the least number of atoms?
1. 1.0 g of oxygen gas (ie. O2).
2. 1.0 g of sulphur (ie. S8).
3. 1.0 g of water vapor (ie. H2O).
4. 1.0 g of liquid water (ie. H2O).
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Slide 57 of 23
Hg gas has a density of roughly 14 g mL-1.
Without using a calculator, estimate the number
of Hg atoms in a 100 mL sample. NA = ~6x1023
mol-1 and the molar mass of Hg is ~200 g mol-1.
1. 1022 atoms
1023 atoms
2. 1023 atoms
1024 atoms
3. 1024 atoms
1025 atoms
4. 1025 atoms
1026 atoms
5. 1026 atoms
1027 atoms
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Slide 58 of 23
Hg gas has a density of roughly 14 g mL-1.
Without using a calculator, estimate the number
of Hg atoms in a 100 mL sample. NA = ~6x1023
mol-1 and the molar mass of Hg is ~200 g mol-1.
1. 1022 atoms
1023 atoms
2. 1023 atoms
1024 atoms
3. 1024 atoms
1025 atoms
4. 1025 atoms
1026 atoms
5. 1026 atoms
1027 atoms
Copyright © 2011 Pearson Canada Inc.
Slide 59 of 23
The Snap Lake diamond mine in the North West
Territories, Canada, is expected to produce 1.5
million carats of diamond per year. Given that
naturally occurring diamond has density 0f 3.15 g
cm-3 to 3.53 g cm-3 and 1 carat = 200mg,
estimate, without using a calculator, the number
of C atoms mined in the form of diamond per
year. NA = ~6x1023 mol-1 and the molar mass of
C is ~12 g mol-1.
1. 1027 atoms
1028 atoms
2. 1028atoms
1029 atoms
3. 1031 atoms
1032 atoms
4. 1029 atoms
1030 atoms
5. 1026 atoms
1027 atoms
Copyright © 2011 Pearson Canada Inc.
Slide 60 of 23
The Snap Lake diamond mine in the North West
Territories, Canada, is expected to produce 1.5
million carats of diamond per year. Given that
naturally occurring diamond has density 0f 3.15 g
cm-3 to 3.53 g cm-3 and 1 carat = 200 mg,
estimate, without using a calculator, the number
of C atoms mined in the form of diamond per
year. NA = ~6x1023 mol-1 and the molar mass of
C is ~12 g mol-1.
1. 1027 atoms
1028 atoms
2. 1028atoms
1029 atoms
3. 1031 atoms
1032 atoms
4. 1029 atoms
1030 atoms
5. 1026 atoms
1027 atoms
Copyright © 2011 Pearson Canada Inc.
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