1 C Introduction to Nuclear Chemistry.ppt

Nuclear Chemistry

1. Intro to Nuclear Chemistry
Chemistry
Mrs. Coyle
http://www.chem.orst.edu/graduate/pics/Reactor.jpg

2. How does a nuclear reactor work?
http://www.lanl.gov/science/1663/images/reactor.jpg

3. How does a small mass contained
in this bomb cause……
•Nuclear
Bomb of
1945
known as
“fat man”
http://www.travisairmuseum.org/assets/images/fatman.jpg

4. …this huge nuclear explosion?
http://library.thinkquest.org/06aug/01200/Graphics/705px-Nuclear_fireball.jpg

5. Is there radon in your basement?
http://a.abcnews.com/images/Blotter/abc_1radon_ad_070625_ssh.jpg

6. Notation

7. Nucleons
•Protons and Neutrons

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

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

10. H H H
http://education.jlab.org/glossary/isotope.html

11. Isotopes of Carbon

12. •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.
Radioactive Isotopes

13. Marie Curie: born 1867, in Poland
as Maria Sklodowska
•Lived in France
•1898 discovered the
elements polonium and
radium.
http://www.radiochemistry.org/nuclearmedicine/pioneers/images/mariecurie.jpg

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 
•Beta 
•Gamma 

16. Emission of alpha particles  :
•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.
Alpha Decay

17. Alpha Decay
Uranium Thorium

18. Alpha Decay
http://education.jlab.org/glossary/alphadecay.gif

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

20. Beta Decay
•Beta particles : electrons ejected from the
nucleus when neutrons decay
n -> p
+
+
-

•Beta particles have the same charge and
mass as "normal" electrons.
•Can be stopped by aluminum foil or a
block of wood.

21. Beta Decay

22. Beta Decay
Thorium Protactinium

23. •Gamma radiation  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.
Gamma Decay

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

26. Which is more penetrating? Why?

29. Part II
•Nuclear Stability
•Half-Life

30. Nuclear Stability
•Depends on the neutron to proton ratio.

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

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

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

34. Example:
C  N + e
In N-14 the ratio of neutrons to protons is 1:1
14
7
-1
014
6

35. •Nuclei with atomic number > 83 are
radioactive

36. Radioactive Half-Life (t
1/2 ):
•The time for half of the radioactive nuclei
in a given sample to undergo decay.

37. Common Radioactive Isotopes
Isotope Half-Life Radiation
Emitted
Carbon-14 5,730 years 
Radon-222 3.8 days 
Uranium-235 7.0 x 108 years 
Uranium-238 4.46 x 109 years 

38. 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.

39. Graph of Amount of Remaining
Nuclei vs Time
A=A
oe
-t
A

40. 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? Answer:50 g
• How many grams are left after two half-
lives?

41. Problem
A sample of 3x10
7
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:1.2x10
5
atoms