1. December 6, 2016
What do you know about nuclear energy or reactions? List at least one thing!
Announcements:
University of Texas due date is extended to Tuesday, Dec 13th at 11:59 p.m.
Test will be Tuesday.
Busy weeks ahead- Keep your head in the game!!

2. Goals To explain the difference between fusion and fission
To describe half life and solve problems using half life

3. Nuclear Chemistry
An element can have both stable and unstable isotopes
Ex:
C-12 is stable so there is no nuclear decay (equal #s of p+ and n0)
C-14 is unstable and radioactive

4. Nuclear Chemistry
A special force called the strong nuclear force holds the p and the n in the nucleus together. This force occurs over a very short distance.

5. Nuclear Chemistry
Because of the strong nuclear force, the n and p attract other n and p.
*n have no charge and they do not repel each other or the protons.
*p repel each other with the electric force and attract each other with the strong nuclear force.

6. Nuclear Chemistry
In stable nuclei, the attractive forces (strong nuclear) are stronger than the repulsive forces (electric).

7. Nuclear Fission
Fission- The process by which a nucleus splits into two or more smaller fragments, releasing neutrons and energy.
The production of lighter nuclei from heavy nuclei
Used in nuclear power plants

8. Nuclear Fission
When U-235 is bombarded by neutrons, the products of the reaction include 2 lighter nuclei that include Ba and Kr together with neutrons and energy
Each dividing nucleus releases about x joules of energy.

9. Nuclear Fission
Some of the mass of the particles before the fission reaction is turned into energy after the reaction.

10. Nuclear Fission matter  energy mass-energy equation
E=mc2 Einstein
A small loss of mass results in a great amount of energy that is given off.

11. Nuclear Fusion
Fusion – The process in which light nuclei combine at extremely high temperatures, forming heavier nuclei and releasing energy.
Energy is also obtained during the fusion process

12. Nuclear Fusion Stars and Sun: Energy is produced when H nuclei combine
We need a large amount of energy to start a fusion reaction so that the H nuclei can be brought together and overcome the electric forces
This energy is provided by the high temperature
Often called thermonuclear fusion

13. Homework Part 1 Read the article and answer the questions Part 2
Number 3: How is fusion different from fission?
Number 5: Change Fission to Fusion in the second part of the question
Number 8: Challenge question, use the box of chemical reactions (bottom right) on the information page to help you out

14. December 7, 2016 How is nuclear fusion different from nuclear fission?
What causes elements to be “radioactive”?

15. Goals
To describe half life and solve problems using half life

16. Radioactive Decay Rates
Half life- The time required for half of the sample of radioactive nuclei to decay.

17. Radioactive Decay Rates
1st half life  ½ sample remains unchanged
2nd half life-> ¼ sample remains unchanged
3rd half life -> 1/8 sample remains
4th half life - > 1/16 sample remains
Eventually the entire sample will decay

18. Radioactive Decay Rates
2. With each successive half life, half of the remaining sample decays to form another element.
Different radioactive isotopes have different half lives.
Half lives can last from nanoseconds billions of years

19. Radioactive Decay Rates
3. If we know how much of the isotope is present at the beginning, we can predict how old the object is.
Rocks 40K decays to 40Ar.
The ratio of 40K to 40Ar is smaller in older rocks
( We have more 40Ar than 40K)

20. Radioactive Decay Rates
c. We can look at the ratios between C-12 and C-14 to determine the age of animal remains or plant remains.

22. * Since the half life is in min
EXAMPLE:
Thallium-208 has a half-life of min. How long will it take for g to decay to 7.50 g?
To do half life problems, make a chart with 4 columns
Number of Half Lives
Time (Min*)
* Since the half life is in min
Amount Remaining (g)
% Remaining
0 (START)
0 (no time has gone by)
120 g (given in problem)
100% (we have ALL of it!) 1
= 3.053
120/2 = 60
100% /2 = 50% 2
= 6.106
60/2 = 30
50%/2 = 25% 3
= 9.159
30/2 = 15
25%/2 = 12.5% 4 =
15/2 = 7.5
12.5%/2 = 6.25%

23. EXAMPLE:
What is the half-life of a g sample of nitrogen-16 that decays to 12.5 g of nitrogen- 16 in 21.6 s?
To get to 12.5 g, it takes 3 half lives. The time is 21.6 s.
Take the time and divide it by the number of half lives to determine how long one half life is.
21.6 s / 3 half lives =
Check your work by filling in the rest of the table
7.2 s for each half life
Number of Half Lives
Time (s)
Amount Remaining (g)
% Remaining
100 g (given in problem)
100% (we have ALL of it!)
0 (START)
0 (no time has gone by) 1
50 g
50% (1/2)
7.2 2
14.4
25 g
25% (1/4) 3
21.6 (given in problem)
12.5 g (stop)
12.5% (1/8)

24. Homework
Part 3 of HW pkt

25. December 8, 2016
Half-Life Lab

26. December 9, 2016 Announcements Check homework packet 1-4 Notes
Quizlet up today
Do not forget U of T due Friday

27. Goals To explain fusion and fission
To describe the three types of radioactive decay
To describe benefits and drawbacks of nuclear energy

28. What are the three types of radioactive decay?
Alpha
Structure: 2 protons and 2 neutrons
Symbol: He
When alpha particle is given off:
Mass number: -4
Atomic number: -2 4 2

29. What are the three types of radioactive decay?
2. Beta
Structure: neutron is changed into a proton and electron; the electron is then given off
Symbol: e
When beta decay occurs:
Mass number: no change
Atomic number: +1 -1

30. What are the three types of radioactive decay?
3. Positron Emission (Beta Capture)
Structure: particle similar to e- in mass, but positive charge
Symbol: e
When positron emission occurs:
Mass number: no change
Atomic number: -1 +1

31. Gamma (Most dangerous to humans)
- occurs when nucleus has too much energy, so it “settles down”
- when it settles, it releases energy in the form of a PHOTON

32. Notes: Benefits
Not a lot of materials to start reaction that gives off a lot of energy, so cheaper
Materials last a while
Clean waste products (water vapor is all that’s released to air)
Others?

33. Notes: Drawbacks Dangerous (Chernobyl, Three Mile Island)
Radioactive wastes
Others?

34. Homework
Complete Part 5 and 6 of homework packet