1. 4.4 Radioactivity

2. Nuclear Reaction - involves change in nucleus
Radioactivity – substances spontaneously emit radiation.
Element can change into another element.
Occurs because nucleus becomes unstable.
Unstable atoms gain stability by losing energy.
Energy lost by emitting radiation.
Chemical Reaction: change of 1 or more substances into new substances.
atoms are rearranged
nucleus is unchanged

3. Nuclear vs. Chemical Reactions
Nucleus is changed:
Atoms are rearranged:

4. Types of Radiation Type Nature 4 2He +2 Sheet of Paper Beta β -1e 0*
Symbol
Mass
Charge
Nature
Penetra- tion
Alpha 4
2He +2
Helium
Nucleus
Sheet of
Paper
Beta β
-1e 0*
1/1840 -1
From
nucleus
High speed
electrons
Aluminum
Foil
Gamma 0
Electro-
Magnetic
Radiation
Lead
Shielding

5. Penetration of Radiation:

6. Nuclear Equations – Mass numbers & atomic numbers must be conserved.
Alpha emission:
226Ra  222Rn + 4He
alpha particle
Mass # and Atomic # Conserved:  

7. Beta Emission: Ex. Carbon-14 decays to produce a beta particle.
14C  N β
beta

8. Gamma Emission – accounts for most of energy lost during radioactive decay.
Usually accompanies alpha & beta.
238U  234Th + 4He 

9. Nuclear stability – primarily determined by:
Ratio of neutrons to protons.
Size of nucleus.
Atoms with atomic # greater than 83 (Bismuth) are unstable.
Atoms eventually decay to form stable, nonradioactive atoms.

10. Radioactive Decay Series

11. Nuclear Fission (Splitting)
Unstable atoms break apart into smaller ones.
Releases tremendous amounts of energy.
Nuclear power plants (U-235)

12. Nuclear Fusion (Uniting)
Fusing together smaller elements to make larger ones.
Produces all elements larger than He
Fusion releases tremendous amounts of energy. (Greater than fission)
Occurs on the Sun (and stars)
Cleaner method but no current technology for power plants.

13. Nuclear Energy (Fission) Pros: Cons:
Does not cause air pollution
(no CO2 emissions, etc.)
Doesn’t use up
fossil fuel (coal)
Less global warming, acid rain
Limited amount of nuclear fuel (Ex. U-235)
Spent fuel is radioactive
Transportation & storage problems!
Water used in cooling process may cause problems when released to environment.

14. Coal vs. Nuclear Power

15. Pro Con Coal waste has more radiation than spent fuel!
Except for Chernobyl, minimal releases of radiation.
High cost of nuclear power (due to government regulations).

16. 15% power by nuclear 52% by coal power

17. The End
Chain Reaction: Neutrons released start
new reactions: