1. Nuclear Chemistry

2. Introduction to Nuclear Chemistry
Nuclear chemistry is the study of the structure of and the they undergo.
atomic nuclei
changes

3. Chemical vs. Nuclear Reactions
Chemical Reactions
Nuclear Reactions
Occur when bonds are broken
Occur when nuclei emit particles and/or rays

4. Chemical vs. Nuclear Reactions
Chemical Reactions
Nuclear Reactions
Occur when bonds are broken
Occur when nuclei emit particles and/or rays
Atoms remain unchanged, although they may be rearranged
Atoms often converted into atoms of another element

5. Chemical vs. Nuclear Reactions
Chemical Reactions
Nuclear Reactions
Occur when bonds are broken
Occur when nuclei emit particles and/or rays
Atoms remain unchanged, although they may be rearranged
Atoms often converted into atoms of another element
Involve only valence electrons
May involve protons, neutrons, and electrons

6. Chemical vs. Nuclear Reactions
Chemical Reactions
Nuclear Reactions
Occur when bonds are broken
Occur when nuclei emit particles and/or rays
Atoms remain unchanged, although they may be rearranged
Atoms often converted into atoms of another element
Involve only valence electrons
May involve protons, neutrons, and electrons
Associated with small energy changes
Associated with large energy changes

7. Chemical vs. Nuclear Reactions
Chemical Reactions
Nuclear Reactions
Occur when bonds are broken
Occur when nuclei emit particles and/or rays
Atoms remain unchanged, although they may be rearranged
Atoms often converted into atoms of another element
Involve only valence electrons
May involve protons, neutrons, and electrons
Associated with small energy changes
Associated with large energy changes
Reaction rate influenced by temperature, particle size, concentration, etc.
Reaction rate is not influenced by temperature, particle size, concentration, etc.

8. The Discovery of Radioactivity (1895 – 1898):
Roentgen
found that invisible rays were emitted when electrons bombarded the surface of certain materials.
Becquerel accidently discovered that phosphorescent salts produced spontaneous emissions that darkened photographic plates
uranium

9. Antoine Henri Becquierel

11. Radioactive decay Discovered by Antoine Henri Becquerel in 1896
He saw that photographic plates developed bright spots when exposed to uranium metals

12. Radioactive Decay – nucleus decays spontaneously giving off an energetic particle

13. The Discovery of Radioactivity (1895 – 1898):
Marie Curie
isolated the components (uraniumatoms) emitting the rays
– process by which particles give off
– the penetrating rays and particles by a radioactive source
Radioactivity
rays
Radiation
emitted

14. The Discovery of Radioactivity (1895 – 1898):
polonium
identified 2 new elements, and on the basis of their radioactivity
These findings Dalton’s theory of indivisible atoms.
radium
contradicted

15. Marie Sklodowska Curie with her daughter, Irene.

16. The Discovery of Radioactivity (1895 – 1898):
Isotopes
same
– atoms of the element with different numbers of
– isotopes of atoms with nuclei (too / neutrons)
– when unstable nuclei energy by emitting to attain more atomic configurations ( process)
neutrons
Radioisotopes
unstable
many
few
Radioactive decay
lose
radiation
stable
spontaneous

17. Alpha radiation Composition – Alpha particles, same as helium nuclei
Symbol – Helium nuclei, He, α
Charge – 2+
Mass (amu) – 4
Approximate energy – 5 MeV
Penetrating power – low (0.05 mm body tissue)
Shielding – paper, clothing 4 2

18. Beta radiation Composition – Beta particles, same as an electron
Symbol – e-, β
Charge – 1-
Mass (amu) – 1/1837 (practically 0)
Approximate energy – 0.05 – 1 MeV
Penetrating power – moderate (4 mm body tissue)
Shielding – metal foil

19. Gamma radiation Composition – High-energy electromagnetic radiation
Symbol – γ
Charge – 0
Mass (amu) – 0
Approximate energy – 1 MeV
Penetrating power – high (penetrates body easily)
Shielding – lead, concrete

22. Ionizing power and penetrating power: an analogy.

23. Positron radiation
Composition – Positron particles, opposite of an electron
Symbol – e+, β+
Charge – 1+
Mass (amu) – 1/1837 (practically 0)

24. Neutron Composition –a neutron Symbol – n, n Charge – 0 Mass (amu) – 1

25. Proton Composition – hydrogen nuclei Symbol – hydrogen nuclei, H, p
Charge – 1+
Mass (amu) – 1 1 + 1

26. Types of radioactive decay
alpha particle emission
beta emission
positron emission
electron capture
gamma emission

27. Alpha emission or decay – giving off an alpha particle

28. Beta Particle emission or decay. - giving off a beta particle

29. electron capture – attaching an electron

30. Practice
218 Po 84 e -1
235
92 U
1 e

31. mass # atomic # Chemical Symbols C neutrons mass # atomic #
A chemical symbol looks like…
To find the number of , subtract the
from the
mass # 14 C
atomic # 6
neutrons
mass #
atomic #

32. Half-Life Half-life time half
is the required for of a radioisotope’s nuclei to decay into its products.
For any radioisotope,
# of ½ lives
% Remaining
100% 1
50% 2
25% 3
12.5% 4
6.25% 5
3.125% 6
1.5625%

33. Half-Life

34. Half-Life
For example, suppose you have 10.0 grams of strontium – 90, which has a half life of 30 years. How much will be remaining after120 years?  
Draw it out

35. initial mass mf = mi x (0.5)n mass final # of half-lives
Half-Life
Or an equation!
initial mass
mf = mi x (0.5)n
mass final
# of half-lives

36. Half-Life
For example, suppose you have 10.0 grams of strontium – 90, which has a half life of 30 years. How much will be remaining after120 years?
Use the formula:

37. What if you need to find the half life ?
Strontium 90 has a half life of 30 years. If there is 100 grams today, how long would it take to have 10 grams remaining
100  50  25  12.5  6.25
10 = 100 x 0.5n
.1 = 0.5n
n= log .1 / log .5
n = 3.32 n is never the answer
30 x 3.32 = 99.6 years

38. Nuclear Fission Fission splitting two equal Chain split slowly
of a nucleus
- Very heavy nucleus is split into approximately fragments
reaction releases several neutrons which more nuclei
- If controlled, energy is released
(like in ) Reaction control depends on reducing the of the neutrons (increases the reaction rate) and
extra neutrons ( creases the reaction rate).
two
equal
Chain
split
slowly
nuclear reactors
speed
absorbing de

39. Nuclear Fission
- 1st controlled nuclear reaction in December st uncontrolled nuclear explosion occurred July
- Examples – atomic bomb, current nuclear power plants

41. Cooling towers of a nuclear power plant.
© 2003 John Wiley and Sons Publishers
Courtesy David Bartruff/Corbis Images
Cooling towers of a nuclear power plant.

42. Construction of a tunnel that will be used for burial of radioactive wastes deep within Yucca Mountain, Nevada.

43. Disposal of radioactive wastes by burial in a shallow pit.

45. Nuclear Fusion Fusion combining light single + + inexpensive
of a nuclei
- Two nuclei combine to form a heavier nucleus
- Does not occur under standard conditions ( repels )
- Advantages compared to fission ,
- Disadvantages - requires amount of energy to , difficult to
- Examples – energy output of stars, hydrogen bomb, future nuclear power plants
light
single + +
inexpensive
no radioactive waste
large
start
control

46. Applications Medicine Chemotherapy Power pacemakers Diagnostic tracers
Agriculture
Irradiate food
Pesticide
Energy
Fission
Fusion

47. X-ray examination of luggage at a security station.

48. An image of a thyroid gland obtained through the use of radioactive iodine

49. Images of human lungs obtained from a γ-ray scan.

50. A cancer patient receiving radiation therapy.