Transcript Nuclear Physics

Chapter
Nuclear Physics
1
Nuclear Radiation
Radioactivity- the processes by which
unstable nuclei achieve stability by releasing
radiation.
Radiation- the penetrating rays and particles
emitted by a radioactive source.
Radioactive Decay- the process in which
unstable nuclei disintegrates.
Radioisotopes- an isotope that has an
unstable nucleus and undergoes radioactive
2
decay.
Types of Radiation
1. Alpha Radiation
 Particle of 2 protons and 2 neutrons
 +2 charge
 Decreases atomic # by 2 and mass by 4
 Very weak, can be stopped by paper or
clothing
4 He
 Symbols:
4


2
2
3
2. Beta Radiation
 Fast moving electrons emitted from the
nucleus
 A neutron in the nucleus decomposes into a
proton and an electron, the electron is
emitted, the proton stays in the nucleus.
 -1 charge
 Does not change the mass, but increases
the atomic number by 1
 Can be stopped by aluminum foil, thin
pieces of wood
0
0
 Symbols:


-1
e
-1
4
3. Gamma Radiation






High energy electromagnetic radiation
given off by a radioisotope.
Not a particle, a wave of energy
Released with alpha and beta radiation
Does not change the mass or atomic
number
Can only be stopped by thick concrete
or lead.
Symbol:
γ
5
l
Write nuclear equations for the
following:
1) Alpha decay of nitrogen-14
l
2) Beta decay of rubidium-87
l
3)Alpha and gamma decay of gold-185
6
Write nuclear equations for the
following:
4)
Beta and gamma decay of uranium-238
5)
Beta decay of sodium-24
6)
Alpha decay of polonium-210
7
Nuclear Transformations
Reasons for a nucleus may be unstable:
1. Too many neutrons relative to the number
of protons.
 To achieve stability, the nucleus
will emit a beta particle.
 Increases the atomic number by
one, but does not change the
mass
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2. Too few neutrons relative to
the number of protons.
To reach stability a proton is
converted into a neutron by
“capturing” an electron
decreases the atomic number
by 1, but does not change the
mass
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To reach stability a proton is
converted into a neutron and a
particle with the mass of an
electron but with a positive
charge (positron) is released.
Decreases the atomic number
by 1, but does not change the
mass
10
3. Too many protons and neutrons.
 All elements with an atomic
number greater than 83 are
radioactive
 To achieve stability most will
emit alpha particles.
 decreases the atomic number
of 2 and the mass by 4
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Half-Life- the time required for one-half of
the nuclei of a radioisotope sample to
decay to products.
Transmutation- the conversion of an atom of
one element to an atom of another
element.
Transuranium Elements- all elements with an
atomic number greater than 92
• all are radioactive
• all are synthetic
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Fission and Fusion of Atomic Nuclei
Fission-the splitting of an atom into smaller
fragments
13
Nuclear Fusion- nuclei combine to produce a
nucleus of greater mass
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Radiation and Your Life
Ionization radiation- radiation with enough
energy to knock electrons off some atoms
of the bombarded substance to produce
ions
Detecting Radiation
Geiger Counter-a gas-filled tube used to detect
the presence of radiation
-detects beta radiation best
Using Radiation
1)
Neutron Activation Analysis
2)
Radioisotopes Tracers
3)
Diagnosis of Diseases
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4)
Treatment of Diseases
Scintillation counter- uses a specially coated
phosphorus surface to detect radiation.
-detects all types of radiation
Film badge- several layers of photographic film
covered with black lightproof paper encased
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