1. Nuclear Chemistry Fusion and Fission

2. Nuclear Fission
The splitting of a nucleus into smaller fragments is called nuclear fission.
Heavy atoms (mass number>60) tend to break into smaller atoms, thereby increasing their stability.
Nuclear fission releases a large amount of energy.

3. Nuclear Fission

4. The Fission Process
A neutron travels at high speed towards a uranium-235 nucleus. U
235 92 n 1

5. The Fission Process
A neutron travels at high speed towards a uranium-235 nucleus. U
235 92 n 1

6. The Fission Process
A neutron travels at high speed towards a uranium-235 nucleus. U
235 92 n 1

7. The Fission Process
The neutron strikes the nucleus which then captures the neutron. U
235 92 n 1

8. The Fission Process
The nucleus changes from being uranium-235 to uranium-236 as it has captured a neutron. U
236 92

9. The Fission Process The uranium-236 nucleus formed is very unstable.
It transforms into an elongated shape for a short time.

10. The Fission Process The uranium-236 nucleus formed is very unstable.
It transforms into an elongated shape for a short time.

11. The Fission Process The uranium-236 nucleus formed is very unstable.
It transforms into an elongated shape for a short time.

12. The Fission Process
It then splits into 2 fission fragments and releases neutrons. n 1
141 56 Ba n 1 92 36 Kr n 1

13. The Fission Process
It then splits into 2 fission fragments and releases neutrons. n 1
141 56 Ba n 1 92 36 Kr n 1

14. The Fission Process
It then splits into 2 fission fragments and releases neutrons. n 1
141 56 Ba n 1 92 36 Kr n 1

15. The Fission Process
It then splits into 2 fission fragments and releases neutrons. n 1
141 56 Ba
Energy n 1 92 36 Kr n 1

16. Nuclear Fission Examples
235 92 + Ba
141 56 n 1 3 Kr 36 U
235 92 + Cs
138 55 n 1 2 Rb 96 37

17. Review: Balancing Nuclear Equations
Mass numbers and Atomic numbers must add up on both sides of the reaction arrow.
100Fm  54Xe + ____ n
256
140
112
46Pd 1 =
For Atomic numbers 100 = X
X = 46
For Mass Numbers: 256 = X + 4
X = 112

18. White Boards
Supply the missing atomic symbol to complete the equation for the following nuclear fission reaction.
1n U Te + ?X n + energy ?

19. Solution
1n U Te + 97Zr n + energy

20. Fission Chain Reactions
One fission reaction can lead to more fission reactions in a process called a chain reaction.
Example - The fission of Uranium-235

21. Chain Reaction of Uranium-235

22. A chain reaction can only occur if the starting material has enough mass to sustain a chain reaction. This amount is called the critical mass.
Nuclear Fission is what occurs in Nuclear Reactors and Atomic Bombs.
The Nuclear reactor is a controlled fission reaction, the bomb is not.
The chain reaction releases a large amount heat and energy that produces an atomic explosion.

24. Nuclear Fusion 4 H + 2 0 e  He + energy
The combining of atomic nuclei to form a larger atom is called fusion
Nuclear fusion occurs in the sun when two nuclei with low mass numbers combine to produce a single nucleus with a higher mass number.
Fusion releases large amounts of energy.
Example:
Energy
4 H e  He + energy 1 4 1 -1 2

25. Nuclear Fusion

26. The Fusion Process H 2 1 H 3 1

27. The Fusion Process H 2 1 H 3 1

28. The Fusion Process H 2 1 H 3 1

29. The Fusion Process H 2 1 H 3 1

30. The Fusion Process

31. The Fusion Process

32. The Fusion Process

33. The Fusion Process

34. The Fusion Process n 1 He 4 2
ENERGY

35. The Fusion Process n 1 He 4 2
ENERGY

36. The Fusion Process n 1 He 4 2
ENERGY

37. The Fusion Process n 1 He 4 2
ENERGY

38. Nuclear fusion is what powers our sun - and all stars.

39. And also - Hydrogen Bombs

40. Fusion
Fusion reactions also release very large amount of energy but require extremely high temperatures to start.
Nuclear fusion also occurs in new stars and is how all of our elements were made. 4
He He  Be + energy 4 8 2 4 2 4 12
He Be  C + energy 8 2 4 6

41. Other Fusion Reactions
Hydrogen Bomb or possible Fusion nuclear reactor reaction
3H + 2H  4He + 1n
New elements discovered:
20Ca Am  115Uup
115Uup  113Uut + 2He 2 1 1 4

42. Remember: Nuclear fission and fusion both occur with an incredible release of energy.

43. Learning Check Indicate if each of the following describes
1) nuclear fission or 2) nuclear fusion.
___ A. a nucleus splits.
___ B. large amounts of energy are released
___ C. small nuclei form larger nuclei.
___ D. hydrogen nuclei react.
___ E. several neutrons are released.

44. Solution Indicate if each of the following is
1) nuclear fission or 2) nuclear fusion.
1 A. a nucleus splits.
1, 2 B. large amounts of energy are released.
2 C. small nuclei form larger nuclei.
2 D. hydrogen nuclei react.
1 E. several neutrons are released.

45. Chemical Reactions Nuclear Reactions
Involve changes in electrons
Acids & Bases, combustion, displacement
The same atoms appear on both sides of the reaction.
Small amount of energy generated
Burning fossil fuels
Nuclear Reactions
Involve changes in the nucleus
Nuclear fusion, nuclear fission
New atoms appear as products of the reaction.
Large amount of energy generated
1 million times more than chemical reactions
Nuclear fusion on the sun
Nuclear fission for reactors

46. Decay vs. Nuclear Reactions
Alpha, beta, and gamma decay occur as ONE atom tries to increase it’s stability by getting rid of a few neutrons, or protons & neutrons.
The product is an alpha, beta, or gamma particle and ONE new atom. There is only ONE thing on the left hand side.
Nuclear reactions involve more than just getting rid of a few protons or neutrons. The new atoms produced are VERY different elements than the reactant.
Nuclear reactions must be started, so there are 2 things on the left hand side.
Nuclear fission: makes 2 or more much smaller atoms
Nuclear fusion: makes 1 much larger atom

47. What are the differences between the 2 above nuclear equations??
Nuclear Fission
Alpha Decay
What are the differences between the 2 above nuclear equations??