Outline Chapter 8a The Nucleus

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Outline Chapter 8a The Nucleus
8-1. Rutherford Model of the Atom 8-2. Nuclear
Structure 8-3. Radioactive Decay 8-4. Half-Life
8-5. Radiation Hazards 8-6. Units of Mass and
Energy
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8-1. J.J. Thompsons Plum Pudding Model of the
Atom
In 1898, British physicist J. J. Thompson
described atoms as positively charged lumps of
matter with electrons embedded in them.
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8-1. Rutherford Model of the Atom
In 1911, an experiment suggested by British
physicist Ernest Rutherford shows that alpha
particles striking a thin metal foil are
deflected by the strong electric fields of the
metal atom's nuclei.
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8-2. Nuclear Structure
The nucleus of ordinary hydrogen is a single
positively charged proton other nuclei contain
electrically neutral neutrons as well as protons.
The number of protons is the atomic number.
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8-2. Nuclear Structure
Isotopes are atoms of the same element that
differ in the number of neutrons in their nuclei.
A nucleus with a particular composition is called
a nuclide and is represented by  ZX where X
chemical symbol, Z atomic number, and A mass
number or the number of protons and neutrons in
the nucleus. A nucleon is a neutron or proton
the mass number of a nucleus is the number of
nucleons (protons and neutrons) it contains.
A
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Isotope Notation
Protons Neutrons Electrons 6 6
6 6 7
6 6 8 6
How many protons, neutrons and electrons in each
of the following protons neutrons
electrons 23Na 14N 38Ar 35Cl 36Cl-1 56Fe
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12
11
7
7
7
18 20 18
17 18 17
17 19 18
26 30 26
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8-3. Radioactive Decay
In 1896, Henri Becquerel discovered that uranium
gives off a penetrating radiation, a property
called radioactivity. Soon after Becquerel's
discovery, Pierre and Marie Curie discovered two
more radioactive elements polonium and radium.
Radioactive decay occurs when a nucleus emits
particles or high frequency em waves.
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Band of Stability
Figure 15.4

• The stable nuclides have approximately equal
  numbers of protons and neutrons (N/Z ratio 1)
  in the lighter elements (Z 1 to 20) and more
  neutrons than protons in the heavier elements
  (N/Z ratio gt 1).

15-
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8-3. Radioactive Decay
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Nuclear Decay
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After Decay

• When an atomic nucleus is unstable, decay brings
  the nucleus to a more stable state
• The final product of nuclear decay is a stable
  element
• This may require numerous decay steps
• Uranium 238 requires 8 alpha decays and 6 beta
  decays to eventually become Lead 206, a stable
  element

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Discovery of Po and Ra
Marie Sklodowska Curie
(1867-1934) Marie, and her husband Pierre,
analyzed a ton of Uranium ore. After removing
the uranium the radioactivity increased. This
led to the discovery of Polonium, more
radioactive than uranium, named after here home
country of Poland. After removing the Polonium
the radioactivity increased again. This led to
the discovery of a small amount in their hand of
Radium, so radioactive that it glowed in the dark.
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8-4. Half Life
The half-life of a radionuclide (radioactive
nuclide) is the time needed for half of an
original sample to decay.
http//www.eserc.stonybrook.edu/ProjectJava/Radiat
ion/
http//www.colorado.edu/physics/2000/isotopes/radi
oactive_decay3.html
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8-5. Radiation Hazards
The SI unit of radiation dosage is the sievert
(Sv) 1 Sv is the amount of radiation having the
same biological effects as those produced when 1
kg of body tissue absorbs 1 J of x-rays or gamma
rays. Maximum dose is 20 mSv per year.
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Predicted Indoor Radon Levels
red zones-greater than 4 pCi/L orange
zones-between 2 and 4 pCi/Lyellow zones-less
than 2 pCi/L

Santa Barbara/ Ventura Countieshighest levels
15-
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Fig.8.6
A radionuclide tracer can be seen here. The
different colors are different amount of tracer
absorption. Cancerous bone absorbs more tracer.
The white spot indicates a tumor.
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8-6. Units of Mass and the Electronvolt
The atomic mass unit (u) is the standard unit of
atomic mass 1 atomic mass unit 1 u 1.66 x
10-27 kg The electronvolt (eV) is the energy unit
used in atomic physics 1 electronvolt 1 eV
1.60 x 10-19 J The megaelectronvolt (MeV) is
equal to 1 million eV 1 megaelectronvolt 1 MeV
106 eV 1.60 x 10-13J The energy equivalent of
a rest mass of 1 u is 931 MeV.
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Outline Chapter 8b The Nucleus
8-7. Binding Energy 8-8. Binding Energy per
Nucleon 8-9. Nuclear Fission 8-10. How a
Reactor Works 8-11. Plutonium 8-12. A Nuclear
World? 8-13. Nuclear Fusion 8-14. Antiparticles
8-15. Fundamental Interactions 8-16. Leptons
and Hadrons
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8-7. Binding Energy
All atoms have less mass than the combined masses
of the particles of which they are composed. The
energy equivalent of the missing mass of a
nucleus is called the binding energy the greater
the binding energy of a nucleus, the more the
energy is needed to break it apart.
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8-8. Binding Energy per Nucleon
The binding energy per nucleon is found by
dividing the total binding energy of the nucleus
by the number of nucleons (protons and neutrons)
it contains the greater the binding energy per
nucleon, the more stable the nucleus.
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8-9. Nuclear Fission
Lise Meitner (1878-1968)
Enrico Fermi (1901-1954)
A chain reaction is a series of fission reactions
spreading through a mass of an unstable
radionuclide such as uranium. When a nucleus
undergoes fission, two or three neutrons are
released and can cause other nuclei to split and
begin a chain reaction. The first chain reaction
was demonstrated by the Italian physicist Enrico
Fermi in Chicago in 1942.
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8-10. How a Nuclear Reactor Works
A nuclear power plant transforms nuclear energy
into electricity. The chain reaction within a
nuclear reactor is controlled by a moderator
which slows down neutrons. Reactors use enriched
uranium as a fuel.
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• Super heated water (enclosed)

Nuclear fuel
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8-11. Plutonium
When nonfissionable U-238 captures a fast
neutron, it eventually forms the fissionable
nuclide of plutonium, Pu-239, which can support a
chain reaction. Plutonium is a transuranium
element, meaning that it has an atomic number
greater than the 92 of uranium. The fissionable
plutonium produced in a uranium-fueled reactor
can be used as a fuel or in nuclear weapons.
Little Boy Fat Man
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Nuclear Bombs
Trinity Bomb TestFirst nuclear bomb
http//www.metacafe.com/watch/400824/trinity_nucle
ar_weapon_test/
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Nuclear Bombs
Hiroshima bomb- Little Boy
Equivalent to 12-15 kilotons of TNT 70,000
killed immediately and 70,000 died afterward.
Half from blast, a third radiation and rest from
radioactivity
Enola Gay
Hiroshima before the bomb.
Hiroshima after the bomb.
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Hiroshima after the blast.
The sky turned pink from gamma rays and abut 15
seconds later the shock wave hit.
Imprint of sitting person from gamma ray
incineration.
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Nagasaki-Fatman bomb
Equivalent to 20-22 kilotons of TNT. About
20,000 killed immediately and another 20,000 died
afterward. A military target that contained a
weapons factory.
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A Nuclear World?
Nuclear energy generates about 21 percent of the
electricity produced in the United States.
Questions of safety, costs, and nuclear waste
disposal have halted construction of nuclear
reactors in the United States.
http//en.wikipedia.org/wiki/Chernobyl_disaster
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A Nuclear World?
Nuclear Power plants locations throughout the
world.
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Fig. 8.22
Disposal of nuclear wastes is a problem. Here a
tunnel is being prepared to store nuclear waste
in Yucca Mountain in Nevada.
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8-12. Nuclear Fusion.
Here an experimental fusion reactor at Princeton
University. This uses powerful magnetic fields
to confine the fusion material. This is called a
tokamak reactor based on a Soviet reactor.
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8-12. Nuclear Fusion.
Nuclear fusion produces tremendous quantities of
energy and has the potential of becoming the
ultimate source of energy on earth.
Pons and Fleishmann at the University of Utah
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8-13. Antiparticles
An antiparticle has the same mass and general
behavior as its corresponding elementary
particle, but has a charge of opposite sign and
differs in certain other respects. When an
antiparticle and its corresponding elementary
particle come together, they undergo
annihilation, with their masses turning entirely
into energy. In the process of pair production, a
particle-antiparticle pair materializes from
energy. Quarks make up protons/neutrons.
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8-14. Fundamental Interactions
1. The strong interaction, which holds protons
and neutrons together to form atomic nuclei. 2.
The electromagnetic interaction, which gives rise
to electric and magnetic forces between charged
particles.
3. The weak interaction, which, by causing beta
decay, helps determine the compositions of atomic
nuclei. 4. The gravitational interaction, which
is responsible for the attractive force one mass
exerts on another.
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8-15. Leptons and Hadrons
Leptons, which are not affected by the strong
interaction, have no internal structure.
Electrons are leptons. Neutrinos are leptons that
have no charge and very little mass. Hadrons,
which are affected by the strong interaction, are
composed of quarks protons and neutrons are
hadrons.
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8-15. Leptons and Hadrons
Physics is trying to bring all theories together
into one THEORY OF EVERYTHING.
Large Hadron Collider at the CERN laboratory
between France and Switzerland, the most powerful
particle accelerator in the world.