1. Intro to Nuclear Chemistry/Nuclear Decay

2. How does a nuclear reactor work?

3. How does a small mass contained in this bomb cause……
Nuclear Bomb of 1945 known as “fat man”

4. …this huge nuclear explosion?

5. Is there radon in your basement?

6. Notation

7. Nucleons
Protons and Neutrons

8. The nucleons are bound together by the strong force.

9. Atoms of a given element with:
Isotopes
Atoms of a given element with:
same #protons
but
different # neutrons

10. H H H

11. Isotopes of Carbon

12. Radioactive Isotopes
Isotopes of certain unstable elements that spontaneously emit particles and energy from the nucleus.
Henri Beckerel 1896 accidentally observed radioactivity of uranium salts that were fogging photographic film.
His associates were Marie and Pierre Curie.

13. Marie Curie: born 1867, in Poland as Maria Sklodowska
Lived in France
1898 discovered the elements polonium and radium.

14. Marie Curie a Pioneer of Radioactivity
Winner of 1903 Nobel Prize for Physics with Henri Becquerel and her husband, Pierre Curie.
Winner of the sole 1911 Nobel Prize for Chemistry.

15. 3 Main Types of Radioactive Decay
Alpha a
Beta b
Gamma g

16. Nuclear Chemistry
Nuclear chemistry involves a change to an atoms nucleus.
Nuclear reactions are accompanied by tremendous energy changes as an unstable isotope spontaneously undergoes changes.
Some types of nuclear decay include:
Alpha decay: An atom emits an alpha particle, thus the nucleus loses 2 protons and 2 neutrons. The atomic number decreases by 2, and the mass number decreases by 4.
Beta decay: An atom emits a beta particle in the form of an electron when a neutron is changed into a proton. The atomic number increases by 1 while the mass number remains the same.
Gamma decay: Usually accompanies alpha or beta emissions as an energy release. Gamma rays cause no change in atomic or mass number since it is a form of energy only.

17. Alpha Decay Emission of alpha particles a : helium nuclei
two protons and two neutrons
charge +2e 
can travel a few inches through air
can be stopped by a sheet of paper, clothing.

18. Alpha Decay
Uranium Thorium

19. Alpha Decay

20. Beta Decay
Beta particles b: electrons ejected from the nucleus when neutrons decay
( n -> p+ +b- )
Beta particles have the same charge and mass as "normal" electrons.

21. Beta Decay
Beta particles b: electrons ejected from the nucleus when neutrons decay
n -> p+ +b-
Beta particles have the same charge and mass as "normal" electrons.
Can be stopped by aluminum foil or a block of wood.

22. Beta Decay

23. Beta Decay
Thorium Protactinium

24. Gamma Decay
Gamma radiation g : electromagnetic energy that is released. 
Gamma rays are electromagnetic waves.
They have no mass.
Gamma radiation has no charge.
Most Penetrating, can be stopped by 1m thick concrete or a several cm thick sheet of lead.

25. Examples of Radioactive Decay
Alpha Decay
Po  Pb + He
Beta Decay p n e
n  p e
C  N e
Gamma Decay
Ni  Ni g
(excited nucleus)

27. Which is more penetrating? Why?

30. Nuclear Stability Half-Life
Part II
Nuclear Stability
Half-Life

31. Nuclear Stability
Depends on the neutron to proton ratio.

32. Band of Stability
Number of Neutrons, (N)
Number of Protons (Z)

33. What happens to an unstable nucleus?
They will undergo decay
The type of decay depends on the reason for the instability

34. What type of decay will happen if the nucleus contains too many neutrons?
Beta Decay

35. Example: C  N + e In N-14 the ratio of neutrons to protons is 1:1 14
C  N e
In N-14 the ratio of neutrons to protons is 1:1 6 -1 7

36. Nuclei with atomic number > 83 are radioactive

37. Radioactive Half-Life (t1/2 ):
The time for half of the radioactive nuclei in a given sample to undergo decay.

38. Common Radioactive Isotopes
Isotope Half-Life Radiation Emitted
Carbon ,730 years b, g
Radon days a
Uranium x 10^8 years a, g
Uranium x 10^9 years a

39. Radioactive Half-Life
After one half life there is 1/2 of original sample left.
After two half-lives, there will be
1/2 of the 1/2 = 1/4 the original sample.

40. Graph of Amount of Remaining Nuclei vs Time
A=Aoe-lt A

41. Example
You have 100 g of radioactive C-14. The half-life of C-14 is 5730 years.
How many grams are left after one half-life?
How many grams are left after two half-lives?

42. Problem A sample of 3x107 Radon atoms are trapped
in a basement that is sealed. The half-life of
Radon is 3.83 days. How many radon atoms
are left after 31 days?
answer:1.2x105 atoms