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. 8-1. J.J. Thompson’s Plum Pudding Model of the Atom.
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8-1. Rutherford Model of the Atom
8-2. Nuclear Structure
8-3. Radioactive Decay
8-5. Radiation Hazards
8-6. Units of Mass and Energy
In1898, British physicist J. J. Thompson described atoms as positively charged lumps of matter with electrons embedded in them.
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.
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.
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.
6 6 6 6 7 6 6 8 6
18 20 18
17 18 17
17 19 18
26 30 26
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.
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 > 1).
Marie Skłodowska 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.
(1943 Marie Currie Movie 2hrs)
The half-life of a radionuclide (radioactive nuclide) is the time needed for half of an original sample to decay.
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.
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
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.
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.
8-7. Binding Energy
8-8. Binding Energy per Nucleon
8-9. Nuclear Fission
8-10. How a Reactor Works
8-12. A Nuclear World?
8-13. Nuclear Fusion
8-15. Fundamental Interactions
8-16. Leptons and Hadrons
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.
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.
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.
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.
LAST, and VERY IMPORTANT is the COOLING of the whole system. This is the ONLY WATER THAT IS NOT COMPLETELY ENCLOSED. Usually comes from a nearby lake or river, recirculated back into the river…
ENCLOSED water circulates around fuel—gets HOT HOT HOT
More ENCLOSED water is heated to boiling,
which turns a turbine—causing the coils of an ELECTRIC GENERATOR to rotate---remember Ampere’s law?
NUCLEAR DECAY PRODUCES HEAT
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
Trinity Bomb TestFirst nuclear bomb
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
Hiroshima before the bomb.
Hiroshima after the bomb.
The sky turned pink from gamma rays and abut 15 seconds later the shock wave hit.
Imprint of sitting person from gamma ray incineration.
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.
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.
Nuclear Power plants locations throughout the world.
Disposal of nuclear wastes is a problem. Here a tunnel is being prepared to store nuclear waste in Yucca Mountain in Nevada.
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.
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
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.
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.
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.
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.