1. NUCLEAR CHEMISTRY nuclear chemistry/physics: processes that occur in
the NUCLEUS—these are
not chemical reactions!

2. Objectives
What is radiation? Understand the meaning of terminology related to radioactivity.
Know the three main types of nuclear radiation.
Be able to write correct nuclear equations.
Understand the concept of penetration power.

3. Radioactivity
1896: Henri Becquerel discovers that uranium affects photographic film.
Marie Curie calls it radioactivity: the process of materials emitting “rays”
radiation: the rays/particles given off by a radioactive source
radioisotope: unstable isotope that emits radiation

4. Three Types of Radiation
a: Alpha (helium nucleus emitted)
Total charge (subscript) and mass (superscript) must be conserved.
b: Beta (electrons emitted as no → p+ + e-)
g: Gamma (high energy EM radiation)

5. Radiation Problems

6. Penetration Power

7. Objectives
Why do atoms decay? Understand the concept of nuclear stability and be able to determine the type of radioactive decay for various isotopes.
Be able to determine the products of various transmutation reactions.

8. Nuclear Transformations
Protons repel, but the nuclear strong force can hold p+ and no together.
Neutrons are needed to supply this force, but a stable p+ to no ratio is necessary.
Elements “decay” to create a stable ratio.

9. Transmutations
transmutation: an atom is converted into a different atom (of a different element)
radioactive decay
*positron: positive electron (antimatter)
*neutrino (v): may be massless
(nucleus is too heavy)
(too many neutrons)
(too many protons)

10. Decay Series

11. Transmutations
bombardment: particles collide with the nucleus to cause transmutations (like bowling!)
Rutherford
The discovery of the p+ and the no were achieved using bombardment.

12. Objectives
How long does it take for a nucleus to decay? Understand the concept of half-life.
Simulate the radioactive decay of an imaginary radioisotope and determine the half-life of the isotope.
Be able to make simple half-life calculations.

13. Half-Life
half-life (T1/2): the time it takes for one-half of the nuclei of a radioisotope to decay to products
64 nuclei → 32 → 16 → 8 → 4 → 2 → 1
If T1/2 = 200 years, it takes six half-lives (1200 years) to decay from 64 to 1.

14. Measuring Nuclear Decay
Fermium has a half-life of days. How much of a 5.2 mg sample of fermium will remain after 365 days?

15. Objectives
What is nuclear energy? Understand the processes of nuclear fission.
Be able to discuss how various technologies employ nuclear fission.

16. Nuclear Fission
fission: the splitting of a large nucleus into smaller fragments
the products have less mass than the reactants
mass is converted into energy (E=mc2)

17. Nuclear Fission Power
Nuclear power plants use controlled nuclear fission to release energy slowly.
Heat creates steam that generates electricity.

18. Fission Reactor Core

19. Three-Mile Island

20. The Fission A-Bomb The WWII bombs used uncontrolled nuclear fission.
Material must have a critical mass to explode.
Test bomb/Nagasaki: implosion of Pu-239
Hiroshima: gun-type with U-235

21. Nuclear Fusion
nuclear fusion: small nuclei combine and release more energy than fission reactions.
The energy (E=mc2) is mostly in the form gamma rays, positrons, and neutrinos.

22. Thermonuclear Weapons
Modern “nukes” use fission to start a fusion reaction.
These weapons are about 100 times more powerful than the A-bomb (1.2 megatons vs. 15 kilotons of TNT).