Atoms and Molecules - Chemeketa Community College
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Transcript Atoms and Molecules - Chemeketa Community College
Chapter 13: Nuclear Chemistry
Radioactivity
Nuclear Equations
Radiation Detection
Half-Life
Medical Applications
Radiometric Dating
Fission & Fusion
CH 104
2-1
CH 104
2-2
Isotopes of Hydrogen
Isotopes = Atoms of the same element but
having different masses.
1
2
3
H
H
H
1
1
1
-
-
-
+
+
Protium
99.99%
Deuterium
0.01%
+
Tritium
Trace %
Average Atomic weight of Hydrogen
= 1.00794 amu
CH 104
2-3
Isotopes of Carbon
12
C
6
-
-
+
+
13
C
6
-
-
-
+
+
+
+ +
-
98.89%
-
+
+
+ +
-
-
+
14
C
6
- -
1.11%
+
-
-
+
-
+
+
+ +
-
-
Trace %
Average Atomic weight of C= 12.011 amu
CH 104
2-4
Radioactive Isotopes
3
H
1
-
14
C
6
+
+
Hydrogen-3
-
-
+
+
+
+ +
Carbon-14
Nucleus is unstable
So falls apart (decays)
Giving radioactive particles
CH 104
2-5
Radioactive Isotopes in Medicine
Diagnose thyroid function 123 I
53
131
I
53
Treat hyperthyroid
(destroys cells)
Destroy tumors
(g radiation)
99m
43 Tc
CH 104
60
Co
27
Diagnose bone, tissue
(most common)
2-6
Alpha Decay
210
Po
84
4
He + +
2
a Particle
+
206
+
Pb
+
82
+
+ +
Transmutation: one element changes to another
210
Po
84
CH 104
4
206
Pb
He
+
82
2
2-7
Beta Decay
14
C
6
+
0
e
-1
+
neutron
CH 104
b Particle
+
+ -+
+
+
1
n
0
-
+
14
N
7
+
+
++
+ +
1
0
H + e
1
-1
proton electron
2-8
Beta Decay
14
C
6
+
0
e
-1
+
CH 104
b Particle
+
+ -+
+
+
14
C
6
-
+
14
N
7
+
+
++
+ +
0
14
+
e
N
7
-1
2-9
Gamma Decay
99m
43 Tc
g decay
+
+
+
+
99m
43 Tc
CH 104
+
+
99
+
Tc
43
99
43
g
Tc
+
+
+
+
+ +
2 - 10
Ionizing Radiation
Radiation knocks off
an electron
An ion
H O H
H O H
H
H
H C H
H
H C H
H
A radical
Ions & radicals cause
damaging chain reactions
CH 104
2 - 11
Geiger Counter
Radiation knocks off
an electron
An ion
Ar
Gas in
instrument
tube
CH 104
Ar
Ions detected
by Counter
2 - 12
Radiation: Penetration through Air
a
b
g
CH 104
+ +
-
2 - 4 cm
200 - 300 cm
500 m
2 - 13
Radiation: Shielding
a
b
Heavy
Cloth
+ +
Paper
Cloth
Pb, thick
concrete
-
g
CH 104
2 - 14
Tissue Penetration Depth
a
b
g
CH 104
+ +
-
0.05 mm
4-5 mm
>50 cm
2 - 15
Nuclear Equations
a: Radium Radon gas in Buildings
226
Ra
88
4
222
+
Rn
He
86
2
4
218
+
Po
He
84
2
CH 104
2 - 16
Nuclear Equations
b: Cancer Treatment
60
Co
27
0
60
+
Ni
e
28
-1
b: Thyroid check & treatment
131
I
53
CH 104
0
131
+
Xe
e
54
-1
2 - 17
Radiation Detection
Activity
Curie (Ci):
# of disintegrations
by of 1g Ra
1 Ci = 3.7 x 1010disintegrations
sec
Becquerel (Bq)
1 Bq = 1 disintegration
sec
CH 104
2 - 18
Radiation Detection
Absorbed Dose
CH 104
2 - 19
Radiation Detection: Biological Effect
Tissue Penetration Depth
a + +
0.05 mm
b
-
g
0.06-5 mm
>50 cm
Radiation Absorbed Dose (Rad) (D):
1 rad = 0.01 J
kg tissue
CH 104
1 rad = 0.0024 cal
kg tissue
100 rad = 1 Gray
2 - 20
Radiation Detection
Biological Damage
CH 104
2 - 21
Roentgen Equivalent for Man (rem)
a
Quality Factor (Q) =
Radiation Weighting factor WR
b
g
WR
20
1
1
Damage (rem) = absorbed dose (rad) X factor
CH 104
1 rem = 1 rad x WR
100 rem = 1 sievert (Sv)
2 - 22
Learning Check
CH 104
2 - 23
Learning Check: Solution
CH 104
2 - 24
Annual Radiation Exposure in USA
Total = 170 - 360 mrem / yr
Cosmic = 26-40 mrem
Air, H2O, Food = 30 mrem
X-rays:
Chest = 50 mrem
Dental = 20
Smoking = 35 mrem
TV/computers = 12 mrem
Radon = 200 mrem
Wood,concrete,bricks = 50 mrem
Ground = 15-30 mrem
CH 104
2 - 25
Annual Radiation Exposure in USA
CH 104
2 - 26
Biological Effects of Radiation
Dose in rem (at one time)
0-25 genetic damage possible but
usually undetected
25-100 decrease # of white blood
cells (temporary)
100-200 mild radiation sickness
(vomit, diarrhea, strong decrease
# white blood cells)
>300 (diarrhea, hair loss, infection)
500 LD50 for humans
CH 104
2 - 27
Biological Effects of Radiation
Dose in rem
300 LD50 for dogs
500 LD50 for humans
800 LD50 for rats
50,000 LD50 for Bacterium
100,000 LD50 for Insects
CH 104
2 - 28
Therapeutic Doses of Radiation
Dose in rem
CH 104
4,500
5,000 – 6,000
Lymphoma
Skin cancer
6,000
Lung cancer
6,000 – 7000
Brain Tumor
2 - 29
FDA approved killing
of bacteria with:
0.3 – 1 kGy ionizing
radiation from
Co-60 or Cs-137
(gamma producers)
CH 104
2 - 30
Half-Life
t1/2 = Time for 1/2 sample to decay
131
I
53
20 g
CH 104
t1/2 =
8 days
8 days
10 g
5g
2 - 31
Half-Life
I-131
Co-60
Tc-99m
Ra-226
CH 104
8 days
5.3 yrs
6 hrs
1620 yrs
2 - 32
Half-Life
t1/2 = Time for 1/2 sample to decay
131
I
53
20 g
t1/2 =
8 days
8 days
10 g
5g
Youtube: Bill Nye Explains Half Life (1:04)
https://www.youtube.com/watch?v=js7weHZIQ5o
CH 104
2 - 33
Half-Life
How much I-131 will be left after 72 days?
131
I
53
20. g
t1/2 =
8 days
8 days
10. g
5.0 g
72 days 1 half-life = 9 half-lifes
1
8 days
20105 2.51.25.625.3125.156g
CH 104
2 - 34
Learning Check:
Chromium-55 undergoes beta decay wth a
half life of 3.5 minutes.
What is the primary identity of the sample after
decay?
55
+
Cr
24
CH 104
2 - 35
Learning Check: Solution
Chromium-55 undergoes beta decay wth a
half life of 3.5 minutes.
What is the primary identity of the sample after
decay?
0
55
55
Mn + e
Cr
24
CH 104
25
-1
2 - 36
Learning Check:
Chromium-55 undergoes beta decay wth a
half life of 3.5 minutes.
What is the primary identity of the sample after
decay?
0
55
55
Mn + e
Cr
24
25
-1
If you start with 120 g; How much Cr-55 will
be left after 14 minutes?
CH 104
2 - 37
Learning Check: Solution
Chromium-55 undergoes beta decay wth a
half life of 3.5 minutes.
What is the primary identity of the sample after
decay?
0
55
55
Mn + e
Cr
25
24
-1
If you start with 120 g; How much Cr-55 will
be left after 14 minutes?
55
Cr
24
120 g
CH 104
t1/2 =
3.5 min
3.5 min
3.5 min
3.5 min
(7 min
Total)
(10.5 min
Tot)
(14 min
Total)
60 g
30 g
15 g
7.5 g
2 - 38
Natural Decay Series of Uranium-238
What is the product of alpha decay of U-238?
238
U
92
4
234
+
Th
He
90
2
What is the product of beta decay of U-238?
234
Th
90
CH 104
0
234
+
e
Pa
91
-1
2 - 39
Natural Decay Series of Uranium-238
238
92 U
234
90 Th
CH 104
234
90
234
Th
Pa
91
+
4
2 He
0
+
-1 e
2 - 40
Natural Decay Series of Uranium-238
CH 104
2 - 41
Learning Check
CH 104
2 - 42
Learning Check: Solution
CH 104
2 - 43
Radiometric Dating
C-14 dating of artifacts (bones, wood,….);
t½ = 5760 years
14
C
6
0
14
+
e
N
7
-1
Issues:
• Production of C-14 by sun varies in atmosphere.
• 14CO2(g) amounts vary in atmosphere
U-238 Pb-206
U-235 Pb-207
Issues:
• Assumes all Pb was once U
K Ar
(t ½ K-40 = 1.248 x 109 years)
40
2 19 K
Issues:
• Ar(g) solubility
Starting amount of K-40
CH 104 •
40
40
+
Ca
Ar
18
20
2 - 44
Artificial Transmutation
1st by Rutherford (1919)
New elements all artificially made in particle accelerators.
YouTube: How does an atom smashing particle accelerator work? (3:26)
https://www.youtube.com/watch?v=G6mmIzRz_f8
Lego particle accelerator: https://www.youtube.com/watch?v=SdmDb8ozcXc
CH 104
2 - 45
Fission
1
n
0
Splitting atoms for Energy
235
92 U
91
36Kr
236
92 U
+
unstable
Uses:
•Atomic Bomb
•Nuclear Power
CH 104
142
56Ba
2 - 46
Fission
235
92 U
CH 104
2 - 47
Fission
235
92 U
CH 104
2 - 48
Fission
235
92 U
CH 104
2 - 49
Fission
235
92 U
CH 104
2 - 50
Fission
236
92 U
CH 104
2 - 51
Fission
91
36Kr
142
56Ba
CH 104
2 - 52
Fission
New elements all artificially made in particle accelerators.
YouTube: How does an atom smashing particle accelerator work? (3:26)
https://www.youtube.com/watch?v=G6mmIzRz_f8
Lego particle accelerator: https://www.youtube.com/watch?v=SdmDb8ozcXc
CH 104
2 - 53
Fission
Need critical mass of U-235
to sustain chain rxn to
produce enough E for an
explosion
CH 104
2 - 54
Fission
U-235
Nuclear Power plants:
•Controlled fission
•avoids critical mass
CH 104
2 - 55
Fusion
Combining atoms for Energy
2
H
1
Deuterium
+
100,000,000OC
Tritium
+
3
H
1
Uses:
•Sun
•Hydrogen Bomb
CH 104
4
He
2
+ + +
1
n
0
+
> E than from fission
But impractical since
heat too high
2 - 56
Fusion
Making radioactive particles
Add 2 stable nuclei unstable nucleus
CH 104
2 - 57
Learning Check
CH 104
2 - 58
Learning Check: Solution
CH 104
2 - 59
Videos
Video: Frontline NOVA Fukushima: Nuclear Aftershocks (53.41 min)
http://video.pbs.org/video/2187854464/
CH 104
2 - 60
Positron Emission Tomography (PET)
11
C
6
+
+
0 + +
+
+
1
H
1
proton
CH 104
0
e
+1
+
b+ Positron
+
11
0
B
5
+
1
0
n + e
0
+1
+
+
+
neutron positron
2 - 61
Positron Emission Tomography (PET)
11
C
6
+
+
0 + +
+
+
11
C
6
0
e
+1
+
0 electron
e
-1 -
b+ Positron
+
11
0
B
5
+
11
0
e
+
B
5
+1
2g rays
Detectable
g rays image
+
+
+
Shows blood flow
positron
CH 104
2 - 62
Positron Emission Tomography (PET)
11
C
6
+
+
0 + +
+
+
0
e
+1
0
+
e
-1
0
e
+1
positron electron
CH 104
+
0 electron
e
-1 -
b+ Positron
+
11
0
B
5
+
2g rays
Detectable
g rays image
+
+
+
Shows blood flow
2g
gamma
2 - 63