1. Chapter 5: Nuclear Chemistry
Radioactivity
Nuclear Equations
Radiation Detection
Half-Life
Medical Applications

2. Average Atomic weight of Hydrogen
Isotopes of Hydrogen
Isotopes = Atoms of the same element but having different masses. 1 2 1 3 1 H H H + - + - + -
Protium
99.99%
Tritium
Trace %
Deuterium
0.01%
Average Atomic weight of Hydrogen
= amu

3. Average Atomic weight of C= 12.011 amu
Isotopes of Carbon C 6 12 C 6 13 C 6 14 - - + - + - + -
98.89%
1.11%
Trace %
Average Atomic weight of C= amu

4. So falls apart (decays) Giving radioactive particles
Radioactive Isotopes 3 1 H C 6 14 - + + - -
Hydrogen-3
Carbon-14
Nucleus is unstable
So falls apart (decays)
Giving radioactive particles

5. Radioactive Isotopes in Medicine
123 53 I
Diagnose thyroid function
131 53 I
Treat hyperthyroid
(destroys cells) 60 27 Co
Destroy tumors
(g radiation) Tc 43
99m
Diagnose bone, tissue
(most common)

6. Alpha Decay He a Particle Po Pb Po Pb He + 4 2 210 84 + 82 206 210 84

7. - Beta Decay e C b Particle N n H e -1 14 6 + + - + 7 14 1 1 -1 +-1 e - 14 6 C
b Particle +
+ - + N 7 14 1 n 1 H -1 e +
neutron
proton
electron

8. - Beta Decay e C b Particle N N e C -1 14 6 + + - + 14 7 14 14 -1 6 7-1 e - 14 6 C
b Particle +
+ - + N 7 14 14 6 C N 7 14 -1 e +

9. Gamma Decay
99m 43 Tc
g decay + + 99 43 Tc
99m 43 Tc Tc 43 99 g +

10. Radiation knocks off an electron
Ionizing Radiation
Radiation knocks off an electron -
An ion
A radical
Ions & radicals cause damaging chain reactions

11. Radiation knocks off an electron Ions detected by Counter
Geiger Counter
Radiation knocks off an electron -
An ion
Gas in instrument tube
Ions detected by Counter

12. - Radiation: Penetration through Air a b g 2 - 4 cm 200 - 300 cm 500 m+
2 - 4 cm b cm -
500 m g

13. - Radiation: Shielding a b g Heavy Cloth Pb, thick concrete+
Pb, thick concrete
Paper Cloth b - g

14. Tissue Penetration Depth+
0.05 mm
4-5 mm b -
>50 cm g

15. a: Radon gas in Buildings
Nuclear Equations
a: Radon gas in Buildings
226 88
222 4 2 He Ra Rn + 86
218 4 2 He Po + 84
Cancer

16. b: Thyroid check & treatment
Nuclear Equations
b: Cancer Treatment 60 27 Co 60 -1 e Ni + 28
b: Thyroid check & treatment
131 53 I
131 -1 e Xe + 54

17. Radiation Detection Activity Curie (Ci):
# of disintegrations
by of 1g Ra
Curie (Ci):
1 Ci = 3.7 x 1010disintegrations
sec
Becquerel (Bq)
1 Bq = 1 disintegration
sec

18. Radiation Detection
Absorbed Dose

19. - Radiation Detection: Biological Effect Tissue Penetration Depth a b+ a - b g
Tissue Penetration Depth
0.05 mm mm
>50 cm
Radiation Absorbed Dose (Rad) (D):
1 rad = 1 x 10-2 J
kg tissue
1 rad = 2.4 x 10-3 cal
kg tissue

20. - Radiation Detection: Biological Effect Tissue Penetration Depth a b+
0.05 mm mm b -
>50 cm g
Radiation Absorbed Dose (Rad) (D):
1 Gray = 1 J
kg tissue
100 rad = 1 Gray

21. Radiation Detection
Biological Damage

22. Radiation Equivalent for Man (rem)
(relative biological effectiveness) a
RBE 20 1 b g
Damage (rem) = absorbed dose (rad) X factor
1 rem = 1 rad x RBE
100 rem = 1 sievert (Sv)

23. Learning Check

24. Learning Check: Solution

25. Annual Radiation Exposure in USA
Total = 170 mrem / yr
Cosmic = 40 mrem
Air, H2O, Food = 30 mrem
X-rays: Chest = 50 mrem
Dental = 20
Smoking = 35 mrem
TV = 2 mrem
Radon = 200 mrem
Wood,concrete,bricks = 50 mrem
Ground = 15 mrem

26. Annual Radiation Exposure in USA

27. Biological Effects of Radiation
Dose in rem (at one time)
0-25 genetic damage possible but usually undetected
decrease # of white blood cells (temporary)
mild radiation sickness (vomit, diarrhea, strong decrease # white blood cells)
>300 (diarrhea, hair loss, infection)
500 LD50 for humans

28. Biological Effects of Radiation
Dose in rem
300 LD50 for dogs
800 LD50 for rats
50,000 LD50 for Bacterium
100,000 LD50 for Insects
500 LD50 for humans

29. Therapeutic Doses of Radiation
Dose in rem
4, Lymphoma
5,000 – 6,000 Skin cancer
6, Lung cancer
6,000 – Brain Tumor

30. FDA approved killing of bacteria with:
0.3 – 1 kGy ionizing radiation from
Co-60 or Cs-137
(gamma producers)

31. Half-Life I t1/2 = Time for 1/2 sample to decay 131 53 5 g 10 g 20 g
8 days
131 53 I
8 days
5 g
10 g
20 g

32. Half-Life
I days
Co yrs
Tc-99m 6 hrs

33. Half-Life I t1/2 = Time for 1/2 sample to decay 131 53 5 g 10 g 20 g
8 days
131 53 I
8 days
5 g
10 g
20 g
Youtube: Bill Nye Explains Half Life (1:04)

34. + Positron Emission Tomography (PET) C e b+ Positron B H n e 11 6 +1 ++1 e +
b+ Positron + + B 5 11 1 H 1 n +1 e +
proton
neutron
positron

35. - + Positron Emission Tomography (PET) e C e 2g rays b+ Positron-1 e
electron 11 6 C +1 e - +
2g rays
b+ Positron +
Detectable
g rays  image
Shows blood flow + B 5 11 11 6 11 5 B +1 e C +
positron

36. - + Positron Emission Tomography (PET) e C e 2g rays b+ Positron-1 e
electron 11 6 C +1 e - +
2g rays
b+ Positron +
Detectable
g rays  image
Shows blood flow + B 5 11 +1 e -1 e 2g +
positron
electron
gamma

37. Fission Energy Kr U U n Ba Splitting atoms for Energy 91 36 235 92 236n
Energy +
unstable
142 56 Ba
Uses:
Atomic Bomb
Nuclear Power

38. Fission
Need critical mass of U-235 to sustain chain rxn to produce enough E for an explosion

39. Fission U-235 Nuclear Power plants: Controlled fission
avoids critical mass

40. > E than from fission But impractical since heat too high
Fusion
Combining atoms for Energy + 2 1 H 4 2 He 1 n
Deuterium
Energy +
100,000,000OC + +
Tritium 3 1 H +
> E than from fission
But impractical since heat too high
Uses:
Sun
Hydrogen Bomb

41. Radiometric Dating N e C Ar Ca 2 K 14 14 -1 6 7 40 40 40 20 19 18 + +
C-14 dating of artifacts (bones, wood,….);
t½ = 5760 years 14 6 C N 7 14 -1 e +
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 = x 109 years) 40 19 K Ar 18 40 40 20 Ca 2 +
Issues:
Ar(g) solubility
Starting amount of K-40

42. Learning Check

43. Learning Check: Solution

44. Videos
Video: Frontline NOVA Fukushima: Nuclear Aftershocks (53.41 min)

45. 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 24 Cr +

46. 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? 55 24 Cr 55 -1 e Mn + 25

47. 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 24 Cr 55 -1 e Mn + 25
If you start with 120 g; How much Cr-55 will be left after 14 minutes?

48. 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? 55 24 Cr 55 -1 e Mn + 25
If you start with 120 g; How much Cr-55 will be left after 14 minutes? 55 24 Cr
t1/2 =
3.5 min
3.5 min
3.5 min
3.5 min
(7 min
Total)
(10.5 min
Tot)
(14 min
Total)
15 g
7.5 g
60 g
30 g
120 g