1. Nuclear Chemistry
Chapter 25

2. Nuclear Radiation
Section 25.1

3. Nuclear Reactions Occur when nuclei emit particles and/or rays.
Atoms are often converted into atoms of another element.
May involve protons, neutrons, and electrons
Associated with large energy changes.
Reaction rate is not normally affected by temperature, pressure, or catalysts.

4. Wilhelm Roentgen
1895:
When electrons bombarded surface of certain materials, invisible rays were emitted

5. Henri Becquerel
studied minerals that when exposed to sunlight, emit light
phosphorescence
discovered uranium salts (pitchblende)

6. Marie Curie 1867-1934 Marie & Pierre Curie
isolated components emitting rays
identifed Po & Ra

7. MORE HISTORY Rutherford (1871-1937)
identified alpha, beta, and gamma radiation

8. PROPERTIES OF RADIATION
Alpha ()
42He, helium nuclei
Blocked by paper; 6.64 x kg
Slow moving due to mass and charge!
Beta ()
0-1 or 0-1e, electrons
Blocked by metal foil; 9.11 x kg
Fast moving
Emitted from a neutron of an unstable nucleus
Insignificant mass compared with mass of nucleus
Greater penetrating power than alpha particles
Gamma ()
00  , photons
Not completely blocked by lead or concrete; 0 kg
High energy electromagnetic radiation
Almost always accompanies alpha and beta radiation

9. Radioactive Decay
Section 25.2

10. NUCLEAR STABILITY Correlated with atom’s neutron-to-proton ratio.
< 20 atomic number most stable

11. BETA DECAY
Instability of isotope due to too many neutrons relative to its number of protons.

12. ALPHA DECAY
All nuclei with more than 83 protons decay spontaneously

13. POSITRON EMISSION
Positron is a particle with the same mass as an electron but the opposite charge
01 or 01e
During emission, a proton in the nucleus is converted to a neutron and a positron
11p --> 10n + 01

14. ELECTRON CAPTURE
Nucleus of an atom draws in a surrounding electron (from lowest energy level)
Captured electron combines with a proton to form a neutron
11p e --> 10n

15. PROBLEM What particle is formed when
polonium-210 undergoes alpha decay?

16. PROBLEM What particle is formed when
polonium-210 undergoes alpha decay?
21084Po --> massatomic #Po

17. PROBLEM What particle is formed when
polonium-210 undergoes alpha decay?
21084Po --> 42He +

18. PROBLEM What particle is formed when
polonium-210 undergoes alpha decay?
21084Po --> 42He ?
How did I get ?

19. PROBLEM What particle is formed when
polonium-210 undergoes alpha decay?
21084Po --> 42He ?
How did I get ? The numbers must add up the same on both sides of the equation (top #’s =, and bottom #’s =)

20. PROBLEM What particle is formed when
polonium-210 undergoes alpha decay?
21084Po --> 42He ?
How do you determine the element?
By atomic number!

21. PROBLEM What particle is formed when
polonium-210 undergoes alpha decay?
21084Po --> 42He Pb
How do you determine the element?
By atomic number!

22. PROBLEM
What would the decay process of iodine-131 into xenon-131 look like?

23. PROBLEM
What would the decay process of iodine-131 into xenon-131 look like?
13153I --> Xe + ?

24. PROBLEM
What would the decay process of iodine-131 into xenon-131 look like?
13153I --> Xe ?
What type of radiation: 0-1?

25. PROBLEM
What would the decay process of iodine-131 into xenon-131 look like?
13153I --> Xe 
What type of radiation: 0-1? Beta!

26. RADIOACTIVE SERIES
A series of nuclear reactions that begins with an unstable nucleus and results in the formation of a stable nucleus.

27. TRANSMUTATION
Section 25.3

28. TRANSMUTATION
Conversion of an atom of one element to an atom of another element
In all but gamma emission nuclear reactions

29. INDUCED TRANSMUTATION
Striking nuclei with high-velocity charged particles
Must be moving at high speeds to overcome electrostatic repulsion of target atom’s nucleus
Use particle accelerators (“atom smashers”

30. TRANSURANIUM ELEMENTS
Elements immediately following uranium in the periodic table
Atomic number of 93 or greater
Developed in the laboratory by induced transmutation
Radioactive

31. PROBLEM
Write a balanced nuclear equation for the induced transmutation of
aluminum-27 into phosphorus-30 by alpha particle bombardment. A neutron is emitted from the aluminum atom in the reaction.

32. PROBLEM
Write a balanced nuclear equation for the induced transmutation of aluminum-27 into phosphorus-30 by alpha particle bombardment. A neutron is emitted from the aluminum atom in the reaction.
Write all symbols on proper sides of the equation. Make certain numbers add up!

33. PROBLEM
Write a balanced nuclear equation for the induced transmutation of aluminum-27 into phosphorus-30 by alpha particle bombardment. A neutron is emitted from the aluminum atom in the reaction.
Write all symbols on proper sides of the equation. Make certain numbers add up!
2713Al He ---> 10n P

34. PROBLEM 2713Al + 42He ---> 10n + 3015P
Write a balanced nuclear equation for the induced transmutation of aluminum-27 into phosphorus-30 by alpha particle bombardment. A neutron is emitted from the aluminum atom in the reaction.
2713Al He ---> 10n P
How did I know the symbol for a neutron?
A neutron has mass but no nuclear charge!

35. HALF-LIFE
Time required for one-half of a radioisotope’s nuclei to decay into its products.
Exponential decay!
Strontium-90 has a half-life of 29 years.
So, if you had 10 g of this, in 29 years you would have 5 grams left.

36. HALF-LIFE Amount remaining = (initial amount)(1/2)n
n is equal to the number of half lives that has passed OR
Amount remaining = (initial amount)(1/2)T/t 1/2
T is equal to the elapsed time and t 1/2 is the duration of the half-life

37. PROBLEM
Iron-59 is used in medicine to diagnose blood circulation disorders. The half-life of iron-59 is 44.5 days. How much of a mg sample will remain after days?

38. PROBLEM Amount remaining = (initial amount)(1/2)n
Iron-59 is used in medicine to diagnose blood circulation disorders. The half-life of iron-59 is 44.5 days. How much of a mg sample will remain after days?
Amount remaining = (initial amount)(1/2)n
X = (1/2)133.5/44.5

39. PROBLEM
Iron-59 is used in medicine to diagnose blood circulation disorders. The half-life of iron-59 is 44.5 days. How much of a 2,000 mg sample will remain after days?
Amount remaining = (initial amount)(1/2)n
X = (1/2)133.5/44.5
Amount remaining = mg

40. RADIOCHEMICAL DATING
Process of determining an age of an object by measuring the amount of a certain radioisotope remaining in that object
Uranium
Half-life of 4.5 c 109 years
Meteorites; have estimated age of solar system at 4.6 x 109 years
Carbon dating
146C ---> 147N 
Half-life of 5730 years
Limited to accurately dating objects up to 24,000 years of age

41. Fission and Fusion of Atomic Nuclei
Section 25.4

42. ∆E = ∆ mc2 I lied! (kind of…)
For most practical situations, mass is conserved, but…
Energy and mass can be converted into each other!
It has been determined that the mass of the nucleus is always less than the sum of the masses of the individual protons and neutrons that comprise it. (CALLED MASS DEFECT)
The missing mass provides tremendous energy required to bind the nucleus together.

43. NUCLEAR FISSION
Heavier atoms (mass # > 60) tend to fragment into smaller atoms to increase their stability
This is accompanied by a very large release of energy

44. NUCLEAR POWER PLANTS Use fission to generate power
UO2 encased in corrosion-resistant fuel rods
Enriched to contain 3% uranium-235 (meets critical mass to sustain the chain reaction)
Control rods of cadmium or boron absorb neutrons released during the reaction, controlling the fission process
Water circulates throughout the core to carry off the heat generated
This is used to power stream driven turbines which produce electrical power
Dense concrete structure encloses the reactor

45. NUCLEAR POWER PLANTS Drawbacks
Hazardous radioactive fuels and fission products
Limited supply of uranium-235
Where to store spent fuel rods?
Require 20 half-lives to decay to safe levels
Amount of spent fuel for a lifetime/person would equal the size of a basketball

46. NUCLEAR FUSION
Binding together two light (mass # < 60) and less stable nuclei
Capable of releasing very large amounts of energy
The sun!
Requires temperatures of 40,000,000 K!
Can achieve this by atomic explosion (not safe!)
Don’t have materials capable of withstanding these high temperatures

47. ATOMIC BOMB Utilizes principles of fission (uncontrolled!)
Equal to effect of 20,000 tons of TNT

48. HYDROGEN BOMB Never used in warfare
Explosive force 1000 X greater than atomic bomb
Fission reaction triggers a fusion reaction of hydrogen isotopes (deuterium and tritium)
Equal to 15 million tons of TNT

49. IONIZING RADIATION
Radiation energetic enough to ionize matter with which it collides
Detected by:
Geiger counter
Metal tube filled with a gas; gets ionized; creates an electrical current
Scintillation counter
Radiation energizes a phosphorcoated surface that releases bright flashes

50. USES OF RADIATION Neutron activation analysis Radiotracers PET
Determine quality of silicon wafers used in computers
Radiotracers
Trace biological pathways
PET
Imagery used in medical diagnoses
Radiation to kill cancer cells
Irradiation of meats, fruits…