1. Unit 11: Nuclear Chemistry Topic 1: Natural Radioactivity
Objective: Identify the 4 modes of decay, use Table N and O to identify natural radioactive decay and write nuclear equations, identify the similarities and differences between physical, chemical, and nuclear reactions, identify what transmutation is

2. I. Natural Radioactivity and Stability
Nuclear Stability: the larger (more massive) a nucleus is, the harder it is for it to stay together
When a nucleus is ______________________, it gives off decay particles and changes ________________________. This is known as ___________________________
Atoms with an atomic number of 1 through 83 have at least one stable isotope, but…
________________________________________________________
radioactive
from one element to another
Natural decay or natural transmutation
All isotopes of elements above 84 are more reactive and are natural radioisotopes

3. II. Four Modes of Decay
spontaneous disintegration
Natural Radioactivity: _________________________________ of the _________________ of an atom, with the emission of _________________________________
Modes of Decay (See Table ______)
nucleus
particles and/or energy O

4. II. Four Modes of Decay Type of Decay Symbol Charge Mass
Penetration Strength

5. II. Four Modes of Decay Transmutations:
Penetration:
When a nucleus decays into a new and different nucleus (also called radioactive decay)
How far into a material the radioactive particle will go

6. III. Nuclear Equations Types of Reactions:
Physical Reaction: H2O (s)  H2O (l)
Same? Different?
Chemical Reaction: 2H2(g) + O2(g)  2H2O (l)
Nuclear Reaction: 167N 0-1e + 168O
Compound & mass (and charge)
Phases (s  l)
Mass and # of same atoms (and charge)
compounds
Mass and charge
elements

7. III. Nuclear Equations
Natural Transmutations (Decay) always has only ___________________________________
Use Table ____ to identify the type of decay for specific nuclide
Use Table ____ to identify notation of each decay mode
One reactant and two products N O

8. III. Nuclear Equations Show the natural radioactivity decay of:
Francium – 220
2. Gold – 198
3. Neon – 19

9. III. Nuclear Equations How do you balance with nuclear equations?
Show the natural radioactivity decay of:
4. Iodine– 131
5. Uranium– 223
Potassium – 37
How do you balance with nuclear equations?
Sum of charges and mass numbers are balanced

10. Unit 11: Nuclear Chemistry Topic 2: Half-Life
Objective: Solve various half-life problems based on given data.

11. IV. Half-Life Problems
Half-Life: the period of time that must go by for half of the nuclei in the sample to undergo decay.
During a half-life period: half of the radioactive nuclei in a sample decays _________________________
The half-life of many radioactive isotopes can be found on Table_____
Solving half-life problems strategies:
1. Identify what nuclide (isotope) is the problem asking for? (go to table N if necessary)
2. What is the half-life of the nuclide?
3. How much time has passed? How many half lives does this represent? How many cuts in half were there?
4. Cut mass in half the required number of times
to a new, more stable nuclei N

12. IV. Half-Life Problems Examples:
1. What mass of I-131 remains 32 days after a 100 gram sample is obtained?
2. What fraction of 1 gram sample of carbon – 14 would remain after 17,190 years?

13. IV. Half-Life Problems Examples:
3. Analysis of charred wood at a prehistoric campsite reveals that it contains 1/4 of the amount of carbon-14 that is found in living tissues. How old is the campsite?
4. The half-life of Rn-222 (a carcinogenic house pollutant) is 3.8 days. If today your basement contains 20 grams of Rn-222, how much will remain after 19 days, assuming no more leaks in?

14. IV. Half-Life Problems Examples:
5. The half-life of Tc-99m* (used to locate brain tumors) is 6.0 hours. If 10. Micrograms are left after 24 hours, how much Tc-99m was administered?
6. A radioactive sample is placed next to a Geiger counter and monitored. In 20.0 hours, the counter’s reading goes from 500 counts/minute to 125 counts/minute. How long is the half-life?

15. IV. Half-Life Problems Examples:
7. The oldest rocks on Earth have been found to contain 25% of their original mass of U What is the age of these rocks?

16. Unit 11: Nuclear Chemistry Topic 3: Artificial Transmutations
Objective: Write artificial transmutation reactions, identify the similarities and differences between artificial/natural decay, and identify the similarities and differences fission/fusion reactions.

17. V. Artificial Transmutations
Remember when writing/ balancing nuclear reactions: The sum of the charges and mass numbers must be equal on both sides
Example 1: 94 Be _____  C n
Example 2: 2713Al He  n _____
“man made” reaction caused by hitting a nucleus with a high-energy particle, such as a neutron or alpha particle
42 He
3115 P

18. V. Artificial Transmutations
PRACTICE 1 – 5 on the front of Worksheet 3

19. V. Artificial Transmutations
  Similarities and Differences between Natural Transmutations and Artificial Transmutations
Unique to Natural Decay
Common to Both
Unique to Artificial Transmutation
- Single UNSTABLE reactant decays into a decay particle and new, more stable nucleus
- Mass and charge conserved
- STABLE nucleus and particle bullet collide to produce NEW products
- Both form new elements
- Both produce energy
Smaller amount
Larger amount

20. VI. Fission and Fusion
Fission -  
Example: (ANIMATION)
- SPLITTING of a nucleus into smaller nuclei, accompanied by a release of neutrons and large amount of energy (exothermic)
- Commonly used isotopes are Uranium-235 and Plutonium-239
23592U + 10n  9236Kr Ba n + ENERGY

21. 31H + 21H  42He + 10n + ENERGY VI. Fission and Fusion Fusion-
Example: (ANIMATION)
Occurs when nuclei COMBINE to produce a nucleus of GREATER mass
- EXOTHERMIC process (MUCH more energy than fission)
31H + 21H  42He + 10n + ENERGY

22. VII. Where does Energy come from?
Both reactions sacrifice nuclear mass to form energy (E= mc2)
the “missing mass” in a nuclear reaction is called the mass defect and is the energy released in the reaction
VIDEO
How are nuclear power plant works?

23. V. Artificial Transmutations
  Similarities and Differences between Nuclear Fission and Fusion
Unique to Nuclear Fission
Common to Both
Unique to Nuclear Fusion
- SPLITS nucleus to SMALLER particles
Both generate energy the same way (Convert mass  energy)
Less energy
more energy
- COMBINES two small nuclei together to form a LARGER one
- Artificial transmutation
- Used to produce electricity in powerplants
- Used by stars
- Produces essentially no radioactive waste
- Produces radioactive waste

24. Unit 11: Nuclear Chemistry Topic 4: Uses and Dangers of Radioisotopes
Objective: Understand the benefits and risks of nuclear reactions, identify specific uses of common isotopes

25. Uses/benefits of Radioisotopes
- Dating: Carbon – 14 (C-14) is measured in dead organism to find out when it was last alive based on its ½ life
Medical:
Certain radioisotopes are useful because they contain SHORT HALF LIVES and are QUICKLY REMOVED from the body
Iodine – 131 – used to detect and treat thyroid cancer
Cobalt – 60 – emits gamma rays that can destroy cancer
Technetium 99– detects cancerous tumors

26. accidents can release harmful radioactive waste into air and water
Radiation Risks
(WRITE SMALL)
- Large amounts of radiation given off by isotopes can cause serious illness and death and environmental damage.
Nuclear Power Plant:
decay products have LONG half-lives and are difficult to store and dispose of
Chernobyl, Ukraine (1986) (news report)
accidents can release harmful radioactive waste into air and water