Transcript Nuclear Chemistry - Duluth High School

Nuclear
Chemistry
Nuclear Reactions
Nuclear chemistry is the
study of changes in an atom’s
nucleus.
 Reactions that involve a
change in the nucleus of an
atom are called nuclear
reactions.
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Characteristics of Nuclear Reactions
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Occur when nuclei emit particles and/or
rays
Atoms are often converted into atoms of
another element
May involve protons, neutrons, and
electrons
Associated with large energy changes
Reaction rates aren’t normally affected by
temperature, pressure, or catalyst
What Causes Nuclear
Reactions?
The nuclei of some atoms are
unstable and may undergo
several changes.
 Unstable systems gain
stability by losing energy.
 Certain atoms lose energy by
emitting rays and particles
called radiation.
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Related Terms
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This spontaneous emission of radiation
is a process called radioactivity.
The process by which unstable nuclei
emit radiation to lose energy is called
radioactive decay.
Radioisotopes, isotopes of atoms
with unstable nuclei, undergo nuclear
decay.
Types of Radiation
Alpha
-Composed of alpha particles
-Contains 2p+ and 2n⁰
-42He or α
Beta
-Composed of beta particles
-Fast moving e- 0-1β or 0-1e
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Types of Radiation (cont)
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Gamma
-Not deflected by electric or
magnetic fields
-High energy electromagnetic
radiation (not a particle)
-No mass and No charge
-00γ
http://www.mhhe.com/physsci/chem
istry/essentialchemistry/flash/radioa
7.swf
Types of Radiation Summary
Type of
Radiation
Symbol
Charge
Penetrati
on
Ability
Mass
alpha
4
2He
2+
blocked by
paper
heaviest
(4 amu)
beta
0
-1β
1-
blocked by
metal foil
lightest
(1/1840
amu)
gamma
0
0γ
0
not
completely
blocked by
lead or
concrete
none
Nuclear Equations
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Used to express nuclear reactions
Both sides of the equation must have
an equal sum of atomic mass and
atomic numbers
Examples:
235 U  4 He+ 231 Th
92
2
90
37 K  0 β + 37 Ca
19
-1
20
41 Ca  41 Ca + 0 γ
20
20
0
Half-Life
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The time required for one half of a
radioisotope’s nuclei to decay into its
products is called a half-life.
Amt Remaining=(Initial Amt)(1/2)n
-n = # half lives passed
Amt Remaining=(Initial Amt)(1/2)t/T
-t=elapsed time
-T=duration of half life
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Example half-life problems:
- How much of a 100.0g sample of
198Au is left after 8.10 days if its halflife is 2.70 days?
-A 50.0g sample of 16N decays to
12.5g in 14.4 seconds. What is its
half-life?
-The half-life of 42K is 12.4hours.
How much of a 750g sample is left
after 62.0hours?
-What is the half-life of 99Tc if a
500g sample decays to 62.5 g in
639,000 years?
Fission and Fusion
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The splitting of an atoms nucleus into
fragments is called fission.
-Provides energy for nuclear power
plants
http://www.visionlearning.com/library/flas
h_viewer.php?oid=2391&mid=59
The combining of atomic nuclei is called
fusion.
-Fuels the sun
http://www.visionlearning.com/library/flas
h_viewer.php?oid=2747&mid=59