3.1 Internal Structure of
an Atom
Atoms were thought to be indivisible
In about 1900, it was learned that all
atoms release negatively charged
particles (electrons).
If there are negative particles, there must
be positive particles (protons).
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3–1
3.1 Internal Structure of
an Atom
To make mass relationships work, there
had to be neutral particles with about
the same mass as protons (neutrons).
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3–2
Charge and Mass Characteristics of Electrons,
Protons, and Neutrons
Particle
electron
proton
neutron
Mass(amu)
0.00054858
1.0073
1.0087
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Charge
–1
+1
0
3–3
Figure 3.1 The protons and neutrons of an atom are
found in the central nuclear region, or nucleus, and
the electrons are found in an electron cloud outside
the nucleus.
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3–4
3.2 Atomic Number and
Mass Number
# of Protons = Z = Atomic Number
# of Protons identifies the element
# Above element symbol on Periodic Table
# of Electrons = Z for neutral atom
“Protons give an element its identity,
electrons give it its personality”
Darryl Ebbing to Bill Bryson
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3–5
3.2 Atomic Number and
Mass Number
Mass # = # of Protons + # of Neutrons
# of Neutrons = Mass # - # of Protons
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3–6
3.3 Isotopes and
Atomic Masses
It is possible for atoms of the same
element to have different numbers of
neutrons.
These variants on an element are called
isotopes.
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3–7
3.3 Isotopes and
Atomic Masses
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3–8
3.3 Isotopes and
Atomic Masses
Symbols for isotopes of an element:
1
2
H
1
3
H
1
12
H
1
Protium
Deuterium
Tritium*
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13
C
6
14
C
6
C
6
Carbon-12
Carbon-13
Carbon-14*
3–9
3.3 Isotopes and
Atomic Masses
The atomic mass of an element is a
weighted average of the masses of the
isotopes, on a relative scale.
Carbon-12 is defined to have a mass of
exactly 12 atomic mass units (amu).
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3–10
3.3 Isotopes and
Atomic Masses
Atomic Mass of Chlorine:
75.53% of chlorine atoms are Chlorine 35,
atomic mass = 34.97 amu
24.47% of chlorine atoms are Chlorine 37,
atomic mass = 36.97 amu
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3–11
3.3 Isotopes and
Atomic Masses
Atomic Masses are given below the
element’s symbol on the Periodic Table
7
N
Nitrogen
14.0067
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3–12
Chemistry at a
Glance:
Atomic
Structure
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3–13
3.4 The Periodic Law and
the Periodic Table
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3–14
Dmitri Mendeleev
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3–15
The modern Periodic Table. Elements with similar
chemical properties fall in the same vertical column.
PERIODIC TABLE OF THE ELEMENTS
1
17
18
1A
7A
8A
1
1
2
H
H
He
Hydrogen
2
13
14
15
16
Hydrogen
Helium
1.00794
2A
3A
4A
5A
6A
1.00794
4.00260
3
4
5
6
7
8
9
10
Li
Be
B
C
N
O
F
Ne
Lithium
Beryllium
Boron
Carbon
Nitrogen
Oxygen
Fluorine
Neon
6.941
9.01218
10.81
12.011
14.0067
15.9994
18.998403
20.1797
11
12
13
14
15
16
17
18
Na
Mg
Al
Si
P
S
Cl
Ar
Sodium
Magnesium
3
4
5
6
7
8
9
10
11
12
Aluminum
Silicon
Phosphorus
Sulfur
Chlorine
Argon
22.98977
24.305
3B
4B
5B
6B
7B
8B
8B
8B
1B
2B
26.98154
28.0855
30.97376
32.066
35.453
39.948
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
K
Ca
Sc
Ti
V
Cr
Mn
Fe
Co
Ni
Cu
Zn
Ga
Ge
As
Se
Br
Kr
Potassium
Calcium
Scandium
Titanium
Vanadium
Chromium
Manganese
Iron
Cobalt
Nickel
Copper
Zinc
Gallium
Germanium
Arsenic
Selenium
Bromine
Krypton
39.0983
40.078
44.9559
47.88
50.9415
51.996
54.9380
55.847
58.9332
58.69
63.546
65.39
69.72
72.61
74.9216
78.96
79.904
83.80
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
Rb
Sr
Y
Zr
Nb
Mo
Tc
Ru
Rh
Pd
Ag
Cd
In
Sn
Sb
Te
I
Xe
Rubidium
Strontium
Yttrium
Zirconium
Niobium
Molybdenum
Technetium
Ruthenium
Rhodium
Palladium
Silver
Cadmium
Indium
Tin
Antimony
Tellurium
Iodine
Xenon
85.4678
87.62
88.9059
91.224
92.9064
95.94
(98)
101.07
102.9055
106.42
107.8682
112.41
114.82
118.710
121.757
127.60
126.9045
131.29
55
56
57
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
Cs
Ba
*La
Hf
Ta
W
Re
Os
Ir
Pt
Au
Hg
Tl
Pb
Bi
Po
At
Rn
Cesium
Barium
Lanthanum
Hafnium
Tantalum
Tungsten
Rhenium
Osmium
Iridium
Platinum
Gold
Mercury
Thallium
Lead
Bismuth
Polonium
Astatine
Radon
132.9054
137.33
138.9055
178.49
180.9479
183.85
186.207
190.2
192.22
195.08
196.9665
200.59
204.383
207.2
208.9804
(209)
(210)
(222)
87
88
89
104
105
106
107
108
109
110
111
112
114
116
118
Fr
Ra
**Ac
Rf
Db
Sg
Bh
Hs
Mt
(271)
(272)
(277)
(289)
(289)
(293)
Francium
Radium
Actinium
Rutherfordium
Dubnium
Seaborgium
Bohrium
Hassium
Meitnerium
(223)
226.0254
227.0278
(261)
(262)
(266)
(264)
(269)
(268)
*Lanthanide Series
58
59
60
61
62
63
64
65
66
67
68
69
70
71
Ce
Pr
Nd
Pm
Sm
Eu
Gd
Tb
Dy
Ho
Er
Tm
Yb
Lu
Cerium
Praesodymium
Neodymium
Promethium
Samarium
Europium
Gadolinium
Terbium
Dysprosium
Holmium
Erbium
Thulium
Ytterbium
Lutetium
140.12
140.9077
144.24
(145)
150.36
151.96
157.25
158.9254
162.50
164.9304
167.26
168.9342
173.04
174.967
90
**Actinide Series
91
92
93
94
95
96
97
98
99
100
101
102
103
Th
Pa
U
Np
Pu
Am
Cm
Bk
Cf
Es
Fm
Md
No
Lr
Thorium
Protactinium
Uranium
Neptunium
Plutonium
Americium
Curium
Berkelium
Californium
Einsteinium
Fermium
Mendelevium
Nobelium
Lawrencium
232.0381
231.0359
238.0289
237.048
(244)
(243)
(247)
(247)
(251)
(252)
(257)
(258)
(259)
(262)
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3–16
Figure 3.4
In this periodic table, elements 58 - 71
and 90 through 13 (in color) are shown in
their proper positions.
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3–17
3.5 Metals, Nonmetals, etc.
Group (family) of elements--vertical column
Period (row) of elements--horizontal row
Group 1A metals:alkali metals
Group 2A metals: alkaline earth metals
Groups 1A – 8A: representative elements
Groups 1B – 8B: transition metals
Group 7A: halogens
Group 8A: noble gases
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3–18
Properties of Metals, Metalloids, and Nonmetals.
Metals
Metalloids (Semimetals)
Nonmetals
Conductors of Electricity
Semiconductors of
Electricity
Insulators of Electricity
Conduct Heat Well
Conduct Heat Poorly
Metallic Luster
Metallic Luster
No Metallic Luster
Solid at Room Temp
Solid at Room Temp
State Varies with Molar
Mass
Malleable and Ductile
Brittle
Brittle
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3–19
3.6 Electron Arrangement
Within Atoms
Shells: Regions of space that contain electrons
with about the same energy
Numbered 1, 2, 3, 4
Correspond to rows on Periodic Table
Subshells: Regions of space within an electron
shell that contain electrons with exactly the
same energy
s, p, d, and f subshells
Correspond to regions on Periodic Table
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3–20
Figure 3.7
The number of
subshells within a
shell is equal to the
shell number, as
shown here for the
first four shells.
Each individual
subshell is denoted
with both a number
(its shell) and a
letter (the type of
subshell it is in).
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3–21
Figure 3.8
An s orbital has a spherical shape
A p orbital has two lobes
A d orbital has four lobes
An f orbital has eight lobes.
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3–22
Figure 3.9
A summary of the interrelationships
among shells, subshells, and orbitals for
the first four shells.
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3–23
Figure 3.10
The order of filling of
various electron
subshells is shown on
the right-hand side of
this diagram. Above
the 3p subshell,
subshells of different
shells "overlap".
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3–24
Figure 3.11 The order
for filling electron
subshells with electrons
follows the order given by
the arrows in this diagram.
Start with the arrow at the
top of the diagram and
work toward the bottom of
the diagram, moving from
the bottom of one arrow to
the top o the next-lower
arrow.
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3–25
3.7, 3.8 Electron Configurations
And the Periodic Table
Elements within a family (group) have the
same properties because their electron
configurations are similar.
Elements in a family have the same
number of electrons in their outermost
(valence) shells.
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3–26
Figure 3.12 Electron configurations and the
positions of elements in the periodic table.
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3–27
3.10 Nuclear Chemistry
Stable Nuclei: Do not change readily
a.k.a. stable isotopes
Radioactive Nuclei: Undergo radioactive
decay
a.k.a. radioisotopes
Are transformed into different elements as
part of radioactive decay
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3–28
3.10 Nuclear Chemistry
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3–29
3.11 Half-Life
Decay of 80.0 mg of Iodine-131, t1/2 = 8.0 days.
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3–30
Properties of Some Radionuclides.
Isotope
Half-Life
Emission
Use
Hydrogen-3
12 Years
beta
Water content of body
Carbon-14
5600 Years
beta
Radiocarbon dating
Iron-59
45 Days
beta
Anemia, bone marros
Cobalt-60
5.3 Years
beta, gamma
Cancer Therapy
Iodine-123
13 Hours
gamma
Diagnosis of Thyroid Cancer
Iodine-131
8.1 Days
beta, gamma
Treatment of Thyroid Cancer
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3–31
3.12 Types of Radioactivity
Table 3.4
Characteristics of the Three Most
Common Types of Radiation Given
off by Radioactive Atoms.
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3–32
3.13 Radioactive Decay
Equations (XI-1)
Sum of A’s (mass numbers) and Z’s
(atomic numbers) on each side of the
equation must be equal.
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3–33
Alpha () Emission
Helium Nucleus ( particle) is Ejected
4
4

=
2
A
2+
He
2
4
X

A–4

+
Y
Z
2
Z–2
204
4
200
Pb

82
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
2
+
Hg
80
3–34
Beta () Emission
Electron ( particle) is Ejected
0
1–

=
e
–1
1
0
n

1

+
p
0
–1
1
A
0
A
X


+
Y
Z
–1
Z+1
14
0
14
C

6
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
–1
+
N
7
3–35
Gamma () Emission
No change in nucleus
 Rays usually accompany other emissions
Release of energy
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3–36
Positron
1+
( )
Emission
Positively charged electron is emitted
A cyclotron is used to produce F-18
1
0
p

1

+
n
1
1
0
A
0
A
X


+
Y
Z
1
Z–1
18
0
18
F

9
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
1
+
O
8
3–37
3.14 Biological Effects of
Radiation
Called “Ionizing Radiation”
Knocks electrons out of their proper places
Produces reactive species where they don’t
belong
Effect is similar to burning but penetrates
more deeply than heat
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3–38
Figure 3.15
Alpha, beta, and gamma radiations
differ in penetrating ability.
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3–39
Dose Effects
REM = Roentgen Equivalent in Man
1 Roentgen  1.8 x 1012 Ion Pairs
gram of tissue
Dose, in REM’s
0 – 25
Effects
None
25 – 100
Reduction of Blood Cells, No Symptoms
100 – 200
Nausea, Fatigue, Reduction of Blood Cells
200 – 300
Recovery in a Few Months
300 – 600
Some Deaths
600 +
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Most Die
3–40
3.15 Nuclear Medicine
Diagnostic Use: Tracers – “Make Noise”
A radioisotope will do the same chemistry as a
stable isotope, can be used to see if something is behaving normally
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3–41
Properties of Radionuclides
for Diagnoses
Short half-life (just long enough to
prepare and administer)
Stable, nontoxic “daughters”
-Emitter so radiation gets out
( and  just burn)
Reactivity with diseased tissue
“hot spot” or “cold spot”
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3–42
3.15 Nuclear Medicine
Therapy: “Hurt Something”
The radioisotope should get to target organ or
tumor and emit radiation that destroys
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3–43
Properties of Radionuclides
for Therapy
Short half-life (just long enough to
prepare and administer)
Stable, nontoxic “daughters”
 or -Emitter to burn in concentrated
area ( isn’t localized enough)
Reactivity with diseased tissue
“hot spot” not “cold spot”
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3–44
Other Medically Important
Radiation
X-rays
Slightly lower energy than -rays
Produced by beaming -particles on metal
Heavy elements are opaque to x-rays
although they are not radioactive
Iodine, Barium
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3–45
Other Medically Important
Radiation
MRI (Magnetic Resonance Imaging)
Magnetic field and radio-frequency beam
Not ionizing, very low energy
Can see water in tissue; hydrogen is active
nucleus
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3–46
Other Medically Important
Radiation
Ultrasound
High frequency sound energy
Not ionizing, very low energy
Looks for echoes, sound bounces off
hard or stiff surfaces
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