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Models of the Atom
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The
Project
Physics
Course
Transparencies
5
UNIT
Models of the Atom
Published by HOLT, RINEHART and WINSTON, Inc. New York, Toronto
Project Physics
Overhead Projection Transparencies
Unit 5
T35 Periodic Table
T36 Photoelectric Experiment
T37 Photoelectric Equation
T38 Alpha Scattering
T39 Energy Levels — Bohr Theory
m
f-
Periodic Table
T35
Periodic Table
This transparency will be useful in discussions centered around the classification of the elements.
Various overlays highlight chemical families and other pertinent groupings.
Overlay A The modern long form of the Periodic Table. The number below each chemical symbol
represents the element's atomic number. The Roman numerals identify the Groups or
Families. The numbers to the left of Group I identify the Periods.
Overlay B This includes the 62 elements which Mendeleef included in his 1872 classification. His
grouping was, of course, unlike the present long form. Rather it resembled the modern
"short" form of the Table. Remove this overlay.
Overlay C The Alkali Metal Family (Group I).
Overlay D The Halogen Family (Group VII).
Overlay E The Noble Gas Family (Group O).
Overlay F The elements known as the Transition Elements. Remove Overlays C, D. E. and F.
Overlay G The Natural Radioactive Elements. Those which undergo J-decay only are tinted
lighter. Technetium (Tc, Atomic Number 43) is a synthetic element.
Overlay H The Transuranium Elements. These have all been synthesized in the laboratory.
T-35
Periodic Table of the Elements
1
T5
O
'^ 4
0
H
1
II
III
IV
V
VI
VII
He
2
Li
3
Be
4
B
5
c
6
N
7
0
8
F
9
Ne
10
Na
II
Mg
Al
13
Si
14
P
15
s
16
CI
17
Ar
18
K
19
Ca
20
Sc
21
Ti
22
V
23
Cr
24
Mn
25
Fe
26
Co
27
Ni
28
Cu
29
Zn
30
Ga
31
Ge
32
As
33
Se
34
Br
35
Kr
36
Rb
37
Sr
38
Y
39
Zr
40
Nb
41
Mo
42
Tc
43
Ru
44
Rh
45
Pd
46
Ag
47
Cd
48
In
49
Sn
50
Sb
51
Te
52
1
53
Xe
54
Cs
55
Ba
56
1
Hf
72
Ta
73
w
74
Re
75
Os
76
Ir
77
Pt
78
Au
79
Hg
so
TI
8!
Pb
82
Bi
83
Po
84
At
85
Rn
86
Fr
87
Ra
S8
•
•
•
•
La
57
Ce
58
Pr
59
Nd
60
Pm
61
Sm
62
Eu
65
Gd
64
Tb
65
Dy
66
Ho
67
Er
68
Tm
69
Yb
70
Lu
71
Ac
89
Th
90
Pa
91
U
92
Np
93
Pu
94
Am
95
Cm
96
Bk
97
a
98
Es
99
Fm
100
Md
101
No
102
Lw
103
TRK
Periodic Table of the Elements
B
1
1
H
1
Elements Inck
ided in
1872
0
He
1
II
Mendeleef Classification
ill IV V VI VII
2
2
Li
Be
B
c
N
o
F
Ne
3
4
5
6
7
8
9
10
'^
Na
Mg
Al
Si
P
s
CI
Ar
3
II
12
13
14
15
16
17
18
o
^ A
K
Ca
Sc
Ti
V
Cr
Mn
Fe
Co
Ni
Cu
Zn
Ga
Ge
As
Se
Br
Kr
<D 4
Q-
19
20
2
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
c
Rb
Sr
Y
Zr
Nb
Mo
Tc
Ru
Rh
Pd
Ag
Cd
In
Sn
Sb
Te
1
Xe
5
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
6
Cs
Ba
'
Hf
Ta
w
Re
Os
Ir
Pt
Au
Hg
TI
Pb
Bi
Po
At
Rn
55
56
"•
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
7
Fr
Ra
'
/
87
^s
•
•
La
■■ 57
Ce
58
Pr
59
Nd
60
Pm
61
Sm
62
Eu
6i
Gd
64
Tb
65
Dy
66
Ho
67
Er
6%
Tm
69
Yb
70
Lu
71
Ac
■•. 89
Th
90
Pa
9
U
92
Np
93
Pu
94
Am
95
Cm
^6
Bk
97
a
98
Es
99
Fm
100
Md
101
No
102
Lw
103
m
1
1
H
1
11
Periodic Table of the Elements
Alkali
Metals
III IV
Noble.
Gases
V VI
•
•
•
VII
0
He
2
2
Li
Be
\
B
c
N
0
F
Ne
^
3
4
5
6
7
8
9
10
3
Na
Mg
Al
Si
P
S
CI
Ar
II
Q
13
14
15
16
17
18
O
'^ 4
0-
K
Ca
Sc
Ti
V
Cr
Mn
Fe
Co
Ni
Cu
Zn
Ga
Ge
As
Se
Br
Kr
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
5
Rb
Sr
Y
Zr
Nb
Mo
Tc
Ru
Rh
Pd
Ag
Cd
In
Sn
Sb
Te
1
Xe
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
6
Cs
Ba
*•
Hf
Ta
w
Re
Os
Ir
Pt
Au
Hg
TI
Pb
Bi
Po
At
Rn
\j
55
56
•
72
73
74
75
76
77
78
79
so
81
82
83
84
85
86
7
Fr
87
Ra
S8
•
•
•
Halogens
La
57
Ce
58
Pr
59
Nd
60
Pm
61
Sm
62
Eu
6i
Gd
64
Tb
65
Dy
66
Ho
61
Er
6S
Tm
69
Yb
70
Lu
71
Ac
89
Th
90
Pa
91
U
92
Np
93
Pu
94
Am
95
Cm
96
Bk
97
a
9S
Es
99
Fm
100
Md
101
No
102
Lw
103
c
D
E
TT3a5
Periodic Table of the Elements
1
1
H
0
He
1
II
III IV V VI VII
2
2
Li
Be
B
C
N
0
F
Ne
3
4
5
6
7
8
9
10
3
Na
Mg
Al
Si
P
S
CI
Ar
II
0
13
14
15
16
17
18
o
Q.
K
Ca
Sc
Ti
V
Cr
Mn
Fe
Co
Ni
Cu
Zn
Ga
Ge
As
Se
Br
Kr
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
5
Rb
Sr
Y
Zr
Nb
Mo
Tc
Ru
Rh
Pd
Ag
Cd
In
Sn
Sb
Te
1
Xe
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
6
Cs
Ba
■■,
Hf
Ta
w
Re
Os
Ir
Pt
Au
Hg
TI
Pb
Bi
Po
At
Rn
55
56
"•
72
73
74
75
76
77
78
79
so
SI
82
83
84
85
se,
7
Fr
87
Ra
88
•
Rad
ioa
ctiv
eE
em
ent!
La
57
Ac
89
58
Th
90
Pr
59
Pa
91
iNdl
60_
U
92
Pm
61
Np
93
Sm
62
Pu
94
Eu
Al
95
64
Tb
65
Bk
97
a
98
Ho
67
Es
99
Er
es
Fm
100
Tm
69
Md
101
Yb
70
No
102
Lu
71
Lw
103
im
Periodic Table of the Elements
1
1
H
0
He
1
II
III IV V VI VII
2
2
Li
Be
B
c
N
0
F
Ne
3
4
5
6
7
8
9
10
3
Na
Mg
Al
Si
P
S
CI
Ar
II
0
13
14
15
16
17
18
O
« 4
0.
K
Ca
Sc
Ti
V
Cr
Mn
Fe
Co
Ni
Cu
Zn
Ga
Ge
As
Se
Br
Kr
19
20
21
22
23
24
25
26
27
28
29
30
3!
32
33
34
35
36
5
Rb
Sr
Y
Zr
Nb
Mo
Tc
Ru
Rh
Pd
Ag
Cd
In
Sn
Sb
Te
1
Xe
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
6
Cs
Ba
'
Hf
Ta
w
Re
Os
Ir
Pt
Au
Hg
TI
Pb
Bi
Po
At
Rn
55
56
.
72
73
74
75
76
77
78
79
so
81
82
83
84
85
S6
7
Fr
87
Ra
S8
•
•
Rac
lioa
ctiv
eE
lem
ent
s .••'
Transuranium
Elements
La
57
Ac
89
Ce
58
Th
90
Pr
59
iNd
eo
Pa
91
u
92
Pm
61
Np
93
Sm
62''
Pu
94
Eu
Al
95
Gd
64
l
c
Tb
Dy
66
Ho
67
rl
Bk
C»fi
:S
Er
68
Fm
inn
Tm
59
Yb
^0
Md
101
Lu
7!
No Lw
Photoelectric Experiment
T36
Photoelectric Experiment
This transparency can be used to help students visualize the mechanism of the photoelectric effect
and the method of measuring the stopping voltage.
Overlay A A schematic diagram is presented of the photoelectric tube connected to a micro-
ammeter, voltmeter, and a power supply (the empty rectangle above the voltmeter)
The curved emitter is on the right and the collecting rod is on the left. Note that the
circuit is open between the emitter and collector.
Overlay B When the DC power supply provides a positive bias on the collecting rod, the voltmeter
mdicates this positive potential. Photons of a particular frequency are depicted commg
in to the emitter. These photons eject photoelectrons whose paths are illustrated by
arrows. The negative photoelectrons complete the circuit as they accelerate toward the
positive collector and register a current on the micro-ammeter. Remove this overlay
and introduce overlay C.
Overlay C The bias on the collecting rod is now made negative by reversing the terminals on the
power supply. The voltmeter indicates this reversal. Now as photons eject photoelec-
trons thev are slightlv repelled by the negative field surrounding the collecting rod. As a
result only the more energetic photoelectrons get to the collector. The resulting reduc-
tion in current is shown as a lower reading on the ammeter. Remove this overlay and
introduce overlay D.
Overlay D An increased voltage is applied to the collector. When it is sufficiently high it will stop
all photoelectrons (note zero reading on ammeter). This "stopping ^oltage can be
used as a measure of the maximum kinetic energy of the photoelectrons.
T-36
m
i
W
--^■i
Current
Collector Voltage
T-36
+
A
B
Current
Collector Voltage
T'36
A
C
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Current
Collector Voltage
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Current
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4
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itt
+
Collector Voltage
j^ Photoelectric Equation
CO
"^
T37
Photoelectric Equation
This transparency will be useful in analyzing data obtained from experiments dealing with stopping
voltage (see T36). With it you can arrive at the Einstein photoelectric equation.
Overlay A A plot of typical experimental data on the voltage required between the terminals of a
vacuum phototube to reduce the tube current to zero. Remove this overlay and in-
troduce overlay B.
Overlay B Such data imply that the maximum kinetic energy of the emitted photoelectrons is
proportional to the frequency of the incident photons. Remove this overlay and
introduce overlay C.
Overlay C This shows Einstein's interpretation of the data in terms of a "work function" W, an
amount of energy that must be supplied to the electrons before they can escape the
surface. The energy supplied to the electron by the photon is hf, so the emission energy
KE ^ax = hf- W.
>
T-37
Experimental Data on "Stopping Voltages"
3
O
O
©
©
on
©
>
0
no emission
©
light frequency (f )
137
o
it
o
E
O
o
E
0
Inference about Kinetic Energy of Photoelectrons
B
no emission
light frequency (f)
T-37
o
o
0
Einstein's Interpretation of Data
no emission — .*— ►
maximum KE of
photoelectron
energy required
to escape surface
light frequency (f)
Alpha Scattering
oo
T38
Alpha Scattering
This transparency is useful in discussing Rutherford's alpha particle scattering experiment and in
contrasting the Thomson and Rutherford models.
Overlay A A diagrammatic sketch of the Rutherford scattering experiment. A magnifying glass
(not shown) could be moved around the ZnS screen to detect flashes produced by the
alpha particles as they strike the screen.
Overlay B Shows the expected results of the scattering experiment under the assumption that
matter is composed of Thomson atoms. Note that there is very little deflection. Remove
this overlay and add overlay C.
Overlay C These are the results which Rutherford and his co-workers actually observed. The
large deflections required a completely new explanation of the structure of the atom.
Remove overlays A and C and introduce overlay D.
Overlay D Two representations of the Thomson model are shown. The left side depicts large
(lA diameter) spheres of positive electrification with negative electrons imbedded in
them "Uke raisins in a muffin". The right side shows a "potential hill" which positive
alpha particles encounter like marbles rolhng up a slope. Relatisely small deflections
will be caused by this hill.
Overlay E The paths of alpha particles would be only slightly deviated as they pass through
Thomson atoms.
Overlay F The Rutherford modification on the Thomson model will account for the large de-
flections actually observed in experiments. The new model contains a very small positive
nucleus with negative electrons surrounding it. This allows a close approach by alpha
particles and a consequent large deflection. The "potential hill" model is also adapted
to a very steep slope (greatly broadened in the diagram) causing sharp deflections the
closer the particles approach the center. Remove overlays D and E and introduce
overlay G.
Overlay G Alpha particle deflections now match observations.
T-38
- ■•^>-i,"
Gold
Foil
Alpha Particle
Source
^Sm.^:'--:
Zinc Sulfide
Screen
ir»
A
B
Results expected
with Thomson Model
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Zinc Sulfide
Screen
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Alpha Particle
Source
T'38
Results obtained
by Rutherford
A
c
!•■■-■
<^o\d^
Zinc Sulfide
Screen
^
Alpha Particle
Source
T-38
\
+
Thomson Model
TraasB
^-scattering
D
E
I
Thomson Model
T-38
+
Rutherford Model
tT^W
F
(
^-scattering
+
Rutherford Model
Energy Levels — Bohr Theory
as
T39
Energy Levels — Bohr Theory
This transparency will be useful in relating the Bohr theory of energy levels to the spectrum of hydro-
gen. It includes a general treatment of the L\man. Balmer and Paschen Series with a more detailed
coverage of the Balmer Series.
Overlay A On the left the Bohr orbits for hydrogen are drawn to scale (since the radii should
increase according to the expression Rn = 0.5 A li-). An energy level diagram is mcluded
on the right, and a space for spectral Imes across the bottom. Introduce overlays B,
C and D in order.
Overlay B Representations of electron quantum "falls" from higher energy levels to the ground
slate. The resulting emission of the Lyman Series is shown in the spectrum window.
Overlay C The Balmer Series is produced by excited electrons falling back to the second energy
level.
Overlay D The Paschen Series is produced by excited electrons falling back to the third energy
level. Remove overlays B, C and D. Add the remaining overlays in order.
Overlay E The Ha line in the Balmer Series is produced by an excited electron falling from the
third energy level to the second. Note that the scale of the spectral line representation
has been changed.
Overlay F The H.j line in the Balmer Series is produced by an excited electron falling from the
fourth energy level to the second.
Overlay G The H-, line in the Balmer Series is produced by an excited electron falling from the fifth
energy level to the second.
Overlay H The H-, line in the Balmer Series is produced by an excited electron falling from the
sixth energy level to the second.
Overlay I The limit of the Balmer Series is approached as excited electrons from energy levels
higher than /i = 6 fall back to energy level 2.
T-39
T=ai
f49
r 1 r I F
♦
Lyman Series
Balmer Series
ultraviolet
infrared
limits of visible range
ft
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