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NUCLEAR CHEMISTRY
Introduction to Nuclear Chemistry
Nuclear chemistry is the study of the structure of and the they undergo.
atomic nuclei changes
Chemical vs. Nuclear Reactions
Chemical Reactions Nuclear Reactions
Occur when bonds are broken
Occur when nuclei emit particles and/or rays
Chemical vs. Nuclear Reactions
Chemical Reactions Nuclear Reactions
Occur when bonds are broken Occur when nuclei emit particles and/or rays
Atoms remain unchanged, although they may be rearranged
Atoms often converted into atoms of another element
Chemical vs. Nuclear Reactions
Chemical Reactions Nuclear Reactions
Occur when bonds are broken Occur when nuclei emit particles and/or rays
Atoms remain unchanged, although they may be rearranged
Atoms often converted into atoms of another element
Involve only valence electrons
May involve protons, neutrons, and electrons
Chemical vs. Nuclear Reactions
Chemical Reactions Nuclear Reactions
Occur when bonds are broken Occur when nuclei emit particles and/or rays
Atoms remain unchanged, although they may be rearranged
Atoms often converted into atoms of another element
Involve only valence electrons May involve protons, neutrons, and electrons
Associated with small energy changes
Associated with large energy changes
Chemical vs. Nuclear Reactions
Chemical Reactions Nuclear Reactions
Occur when bonds are broken Occur when nuclei emit particles and/or rays
Atoms remain unchanged, although they may be rearranged
Atoms often converted into atoms of another element
Involve only valence electrons May involve protons, neutrons, and electrons
Associated with small energy changes
Associated with large energy changes
Reaction rate influenced by temperature, particle size, concentration, etc.
Reaction rate is not influenced by temperature, particle size, concentration, etc.
The Discovery of Radioactivity (1895 – 1898):
found that invisible rays were emitted when electrons bombarded the surface of certain materials.
Becquerel accidently discovered that phosphorescent salts produced spontaneous emissions that darkened photographic plates
Roentgen
uranium
Antoine Henri Becquierel
Radioactive decay
Discovered by Antoine Henri Becquerel in 1896
He saw that photographic plates developed bright spots when exposed to uranium metals
Radioactive Decay – nucleus decays spontaneously giving off an energetic particle
The Discovery of Radioactivity (1895 – 1898):
isolated the components ( atoms) emitting the rays
– process by which particles give off
– the penetrating rays and particles by a radioactive source
Marie Curieuranium
Radioactivityrays
Radiationemitted
The Discovery of Radioactivity (1895 – 1898):
identified 2 new elements, and on the basis of their radioactivity
These findings Dalton’s theory of indivisible atoms.
poloniumradium
contradicted
Marie Sklodowska Curie with her daughter, Irene.
The Discovery of Radioactivity (1895 – 1898):
– atoms of the element with different numbers of
– isotopes of atoms with nuclei (too / neutrons)
– when unstable nuclei energy by emitting to attain more atomic configurations ( process)
Isotopes sameneutrons
Radioisotopesunstable fewmanyRadioactive decay
radiationlosestable
spontaneous
Alpha radiation
Composition – Alpha particles, same as helium nuclei
Symbol – Helium nuclei, He, α Charge – 2+ Mass (amu) – 4 Approximate energy – 5 MeV Penetrating power – low (0.05 mm body
tissue) Shielding – paper, clothing
42
Beta radiation
Composition – Beta particles, same as an electron
Symbol – e-, β Charge – 1- Mass (amu) – 1/1837 (practically 0) Approximate energy – 0.05 – 1 MeV Penetrating power – moderate (4 mm
body tissue) Shielding – metal foil
Gamma radiation
Composition – High-energy electromagnetic radiation
Symbol – γ Charge – 0 Mass (amu) – 0 Approximate energy – 1 MeV Penetrating power – high (penetrates
body easily) Shielding – lead, concrete
Ionizing power and penetrating power: an analogy.
Types of radioactive decay alpha particle emission beta emission positron emission electron capture gamma emission
Alpha emission
Beta Particle emisson
epn 01
11
10
Review
Type of Radioact
ive Decay
Particle
Emitted
Change in Mass
#
Change in
Atomic #
Alpha α He -4 -2Beta β e 0 +1
Gamma γ 0 0
42
0-1
Chemical Symbols
A chemical symbol looks like…
To find the number of , subtract the
from the
C6
14
mass #
atomic #
mass #atomic #
neutrons
Half-Life
is the required for of a radioisotope’s nuclei to decay into its products.
For any radioisotope,# of ½ lives % Remaining
0 100%
1 50%
2 25%
3 12.5%
4 6.25%
5 3.125%
6 1.5625%
Half-life time half
Half-Life
0 1 2 3 4 5 6 70
10
20
30
40
50
60
70
80
90
100
Half-Life
# of Half-Lives
% R
em
ain
ing
Half-Life
For example, suppose you have 10.0 grams of strontium – 90, which has a half life of 29 years. How much will be remaining after x number of years?
You can use a table:
# of ½ lives
Time (Years)
Amount Remaining (g)
0 0 10
1 29 5
2 58 2.5
3 87 1.25
4 116 0.625
Half-Life
Or an equation!
mt = m0 x (0.5)n
mass remaining
initial mass
# of half-lives
Half-Life
Example 1: If gallium – 68 has a half-life of 68.3 minutes, how much of a 160.0 mg sample is left after 1 half life? ________ 2 half lives? __________ 3 half lives? __________
Half-Life
Example 2: Iron-59 is used in medicine to diagnose blood circulation disorders. The half-life of iron-59 is 44.5 days. How much of a 2.000 mg sample will remain after 133.5 days? ______________
Nuclear Fission
- of a nucleus - Very heavy nucleus is split into
approximately fragments - reaction releases several
neutrons which more nuclei - If controlled, energy is released
(like in ) Reaction control depends on reducing the of the neutrons (increases the reaction rate) and
extra neutrons ( creases the reaction rate).
Fission splitting
slowlysplit
Chainequal
two
Nuclear reactorsspeed
deabsorbing
Nuclear Fission
- 1st controlled nuclear reaction in December 1942. 1st uncontrolled nuclear explosion occurred July 1945.
- Examples – atomic bomb, current nuclear power plants
Cooling towers of a nuclear power plant.
© 2003 John Wiley and Sons Publishers
Courtesy David Bartruff/Corbis Images
Construction of a tunnel that will be used for burial of radioactive wastes deep within Yucca Mountain, Nevada.
Disposal of radioactive wastes by burial in a shallow pit.
Nuclear Fusion
- of a nuclei - Two nuclei combine to form a
heavier nucleus - Does not occur under standard conditions
( repels ) - Advantages compared to fission -
,
- Disadvantages - requires amount of energy to , difficult to
- Examples – energy output of stars, hydrogen bomb, future nuclear power plants
lightcombiningFusion
+ +
start
noradioactivewasteinexpensive
largecontrol
single
Applications
Medicine Chemotherapy Power pacemakersDiagnostic tracers
AgricultureIrradiate foodPesticide
Energy FissionFusion
X-ray examination of luggage at a security station.
An image of a thyroid gland obtained through the use of radioactive iodine
Images of human lungs obtained from a γ-ray scan.
A cancer patient receiving radiation therapy.