Chapter 22 Nuclear Chemistry

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Chapter 22 Nuclear Chemistry
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Nuclear Symbols
Mass number (p no)
Element symbol
Atomic number (number of p)
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Types of Radioactive Decay
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2

• alpha production (a) helium nucleus
• beta production (b)

He
2
0
e
-
1
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Alpha Radiation
Limited to VERY large nucleii.
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Alpha Decay
The release of an alpha particle from an unstable
nucleus.
Alpha particle a high energy particle composed
of two protons and two neutrons a high
energy helium nucleus
4? or 4He
2? or 2He
Properties Of all types of radioactivity, alpha
particles are
the heaviest
the lowest in energy
the least penetrating
the most ionizing
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Alpha Decay
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Alpha Decay
Example The decay of U-238
238U ? 4He
90Th
92U ? 2He
234Th
The effect of alpha decay is to break the
unstable nucleus into two smaller nuclei.
http//nords.com/samples/alphadecay.swf
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Beta Radiation
Converts a neutron into a proton.
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Beta Decay
The release of a beta particle from an unstable
nucleus.
Beta particle a high energy electron ejected
from the nucleus
0? or 0e
-1
-1
Properties Compared to alpha particles, beta
particles are
lighter
higher in energy
more penetrating
less ionizing
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Beta Decay
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Beta Decay
Example The decay of C-14
14C ? 0e
7N
6C ? -1e
14N
The effect of beta decay is to convert a neutron
into a proton.
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Types of Radioactive Decay

• gamma ray production (g)
• positron production
• electron capture (inner-orbital electron is
  captured by the nucleus)

0
e
1
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Gamma Ray Emission
The release of a gamma ray by an excited nucleus.
Gamma rays pure electromagnetic energy
0?
0?
Properties Compared to other types, gamma rays
are
the lightest (having essentially no mass)
the highest in energy
the most penetrating
the least ionizing
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Gamma Ray Emission
Gamma rays are only produced as the by-product of
another type of decay
238U ? 4He
90Th
92U ? 2He
234Th
0?
0?
The effect of gamma ray emission is to release
excess energy from a nucleus that has decayed.
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Positron Emission
The release of a positron from an unstable
nucleus.
Positron a high energy, positively charged
electron ejected from the nucleus the
antiparticle of an electron
0e
1e
Example The decay of O-15
15O ? 0e
7N
8O ? 1e
15N
The effect of positron emission is to convert a
proton into a neutron.
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Annihilation
The process that occurs when a particle and its
antiparticle collide.
0?
0?
0e
-1e 1e ? 2
0e
The effect of annihilation is to convert all of
the mass of both particles into energy.
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Types of Radiation
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Electron Capture(also called k-shell capture)
The capture, or absorption, by the nucleus of an
electron from the lowest level of the atoms
electron cloud.
0e
-1
Example
0?
0?
-
7Be 0e ?
4Be 1e ?
7Li
3Li
The effect of electron capture is to convert a
proton into a neutron.
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Half-life Concept
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Sample Half-Lives
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A Decay Series
A radioactive nucleus reaches a stable state by a
series of steps
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Nuclear Fission and Fusion

• Fusion Combining two light nuclei to form a
  heavier, more stable nucleus.
• Fission Splitting a heavy nucleus into two
  nuclei with smaller mass numbers.

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Nuclear Fission
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Fission
Animation 2
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A Fission Reactor
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Fusion
Animation 1
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Nuclear Fusion