Presentation on theme: "Discovering the Secrets of the Nucleus From a Photographic Mystery to the Atomic Bomb Harnessing the Secrets of the Nucleus Nuclear Energy, Nuclear Medicine,"— Presentation transcript:
Discovering the Secrets of the Nucleus From a Photographic Mystery to the Atomic Bomb Harnessing the Secrets of the Nucleus Nuclear Energy, Nuclear Medicine, and a Nuclear Calendar
Antoine Henri Becquierel.
Radioactive Decay Discovered by Antoine Henri Becquerel in 1896 –He saw that photographic plates developed bright spots when exposed to uranium metals
Types of nuclear reactions Radioactive Decay – nucleus decays spontaneously giving off an energetic particle Nuclear Bombardment – shoot a high energy particle at the nucleus of another atom and watch what happens
Writing Nuclear Equations
The components of α rays, β rays, and γ rays.
The penetrating power of radiation.
Ionizing power and penetrating power: an analogy.
Which component of radioactivity would be stopped by this single page? Which two components would be stopped (completely or almost completely) by this entire book? Which component would pass, almost undiminished, through both this single page and this entire book? QUESTION
Types of radioactive decay alpha particle emission beta emission positron emission electron capture gamma emission
Types of radioactive decay alpha particle emission –loss of a helium nucleus.
Problem Pu-239 (plutonium 239) loses an alpha particle (He nucleus). Write the nuclear reaction
Types of radioactive decay beta emission –A neutron splits into a proton and electron which is spit out as a particle.
Types of radioactive decay positron emission –A proton kicks out positive charge (a positron, +) to become a neutron. –The positron collides with an electron annihilating both and generating energy
Types of radioactive decay electron capture (EC) –an electron (from inner shell) is sucked into the nucleus to combine with a proton – produces a neutron. gamma emission –emission of energy (photon) from an unstable nucleus.
How does an atom’s atomic number change when its nucleus loses a(n): (a) α particle, (b) β particle, (c) ray? How does that atom’s mass number change with the loss of each of these? QUESTION
Pu-239 (plutonium 239) loses an alpha particle (He nucleus). Write the nuclear reaction.
Can we predict types of radioactive decay that will occur? Nuclear particles are held together by a strong attractive force Like electrons, protons are arranged in shells Even numbers of protons and neutrons are most stable. An approximately 1-1 neutron to proton ration is generally most stable Atomic number > 83 is never stable.
Nuclear Bombardment Reactions Transmutation – changing one element to another by shooting a nuclear particle at its nucleus. All transuranium elements (more than 92 protons) were created synthetically in particle accelerators.
Energy of Nuclear Reactions ≠ ≠
A flare ejected from the surface of the sun.
Applications Medicine –Chemotherapy –Power pacemakers –Diagnostic tracers Agriculture –Irradiate food –Pesticide Energy –Fission –Fusion
X-ray examination of luggage at a security station.
Gamma ray analysis of a fitting for a medical device shows it to be free of flaws.
An image of a thyroid gland obtained through the use of radioactive iodine.
Images of human lungs obtained from a γ-ray scan.
A cancer patient receiving radiation therapy.
The Geiger counter.
Nuclear Reactions as an Energy Source Uranium-235, a source of nuclear power.
A typical fission reaction of U-235.
Schematic diagram of the cascading effect of a typical chain reaction initiated by a single neutron.
The world’s first atomic explosion, July 16, 1945 at Alamogordo, New Mexico.
The uranium bomb, 3m (10 ft) long and 0.7 m (2.3 ft) in diameter, was called “Little Boy.”
The operation of fission bombs.
Remains of a building after the explosion of the uranium bomb at Hiroshima, August 6, 1945.
How was a critical mass achieved in the detonation of the U-235 bomb? In the detonation of the Pu-239 bomb? QUESTION
Schematic diagram of a nuclear power plant.
Enrico Fermi built the first atomic pile and produced the first controlled chain reaction on December 2, 1942.
Cooling towers of a nuclear power plant.
The nuclear power plant at Chernobyl, after the accident of April 16, 1986.
Enrichment by gaseous diffusion. Nuclear Power Plants require fuel with ~3% fissionable material, nuclear bombs require ~90% fissionable material. Very difficult to concentrate fissionable material.
Challenges of Nuclear Power Disposal of waste products
Construction of a tunnel that will be used for burial of radioactive wastes deep within Yucca Mountain, Nevada.
Disposal of radioactive wastes by burial in a shallow pit.
When an atom of uranium –235 is bombarded with neutrons, one of the many fission reactions it can undergo produces barium and an additional element (as well as energy and additional neutrons) but no α particles or β particles. With this in mind, and with reference to the periodic table, name the additional element produced in this particular mode of fission. QUESTION
Using the Law of Conservation of Mass and the Law of Conservation of Energy, show why nuclear fission might not be viewed as a chemical reaction. QUESTION
Rate of Nuclear Reactions
If a radioactive isotope has a ½ life of 20 minutes, what percent of the sample will remain after 1 hour? If 75% of a sample decays after 6 hours, what is its half life? If a radioisotope has a half-life of 2 weeks, how long will it take for 99% of the sample to decay?
Applications – Carbon Dating nitrogen in the atmosphere is bombarded by neutrons to form 14 C This carbon is integrated into CO 2 which then enters the food chain
Applications – Carbon Dating
Which of the following can be dated by radiocarbon techniques: (a) a rock; (b) a leather slipper; (c) a wooden boat; (d) a mummified body; (e) a silver spoon. Describe your reasoning. QUESTION
What is the most serious form of damage that could occur if a natural disaster such as a hurricane, a tornado, or an earthquake struck a nuclear power plant? Explain. QUESTION
Describe one advantage of a breeder reactor over a conventional nuclear reactor. Describe one disadvantage. QUESTION
What is the ultimate fate of every radioactive atom now in existence? QUESTION
Name and describe two types of biological damage caused by ionizing radiation. QUESTION
Into what element is an atom of nitrogen-13 transformed when it emits a positron? QUESTION
Which one or more of the detection devices described in this Section would you use if you wished to determine immediately whether the residue left by a spilled chemical is radioactive? Which would you use if you wanted to determine the total, cumulative amount of radiation you might be exposed to in the course of an entire month? QUESTION
Marie Sklodowska Curie with her daughter, Irene.
Ernest Rutherford discovered α rays and β rays.
James Chadwick received the Nobel Prize in physics in 1935 for his discovery of the neutron.
Lise Meitner interpreted Otto Hahn’s experimental observations as confirmation that he had split a uranium nucleus.
J. Robert Oppenheimer and Leslie Groves at the remains of the tower used in the test of the first atomic bomb.
Albert Einstein, he discovered the equation that relates mass and energy.