A detailed study about Nuclear Chemistry

1. Intro to Nuclear Chemistry

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. 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.

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 α
• Beta β
• Gamma γ

16. Emission of alpha particles α :
• 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

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

20. Beta Decay
• Beta particles β: electrons ejected from
the nucleus when neutrons decay
n -> p+
+β-
• 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 γ : 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 + γ
(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 (t1/2 ):
• 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 β, γ
Radon-222 3.8 days α
Uranium-235 7.0 x 108 years α, γ
Uranium-238 4.46 x 109 years α

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=Aoe-λt
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 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