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Radioactivity Notes. The red is what you need to copy. The blue is a new heading. Review…the nucleus. The nucleus is composed of particles called nucleons..__ & __ Neutrons and protons have the same mass, with ___ being slightly greater.
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Radioactivity Notes The red is what you need to copy. The blue is a new heading.
Review…the nucleus • The nucleus is composed of particles called nucleons..__ & __ • Neutrons and protons have the same mass, with ___ being slightly greater. • Neutrons have nearly 2000 times the mass of _____. • protons and neutrons • neutrons • electrons
Review…the atom • The mass of an atom is almost equal to the mass of the _____ alone • Nucleons are bound together by an attractive nuclear force called the ____ force • The positively charged protons in the nucleus hold the negatively charged electrons in their ____ • nucleus • strong • orbits
Review…the atom • The principal role of the neutrons in the nucleus is to act as a sort of ____ to hold the nucleus together • The electrical force acts as a ____ force between protons • The atom needs a certain balance of neutrons and protons for ___ • cement • repulsive • stability
The symbol was created in 1946 UC- Berkeley to represent “activity coming out of a atom”
What is Radioactivity? • Radioactive decay is the process in which an unstable atomic nucleus loses energy by emitting radiation in the form of particles or electromagnetic waves. • There are numerous types of radioactive decay. The general idea: • An unstable nucleus releases energy to become more stable
Radioactive Decay • A neutron is very unstable. A lone neutron will spontaneously decay into a proton + an electron. • If you have a lot of neutrons, within 11 minutes ½ of them will have decayed • Particles that decay are said to be radioactive • A lone neutron is radioactive
Their atoms emit 3 things…alpha, beta particles and gamma rays
Radioactive Isotope • Iodine-131, a beta emitter, is taken as sodium iodide in drinking water. Almost all of it will find its way to the thyroid
Isotopes • They are atoms of the same element that have different numbers of neutrons.
Radioactive Half-Life • The half-life of an element is the time it takes for half of the material you started with to decay Remember, it doesn’t matter how much you start with. After 1 half-life, half of it will have decayed. • Each element decays into a new element • C14 decays into N14 while U238 decays into Pb206 (lead), etc • The half-life of each element is constant. It’s like a clock keeping perfect time
“How much of this element remains after 4 half-lives? Just remember that at the end of one half-life, 50% of the element will remain. Find 50% on the vertical axis, Follow the blue line over to the red curve and drop straight down to find the answer:
Sources of Radioactivity • Primordial - from before the creation of the Earth • Cosmogenic - formed as a result of cosmic ray interactions • Human produced - enhanced or formed due to human actions (minor amounts compared to natural)
Nuclear Fusion - Energy released when two light nuclei combine or fuse • However, a large amount of energy is required to start a fusion reaction: • Need this energy to overcome ________ forces of protons. • Extremely high temperatures can provide start-up energy. repulsion More energy in fusing hydrogen that fission of uranium
Fission • Fission may be defined as the process of splitting an atomic nucleus into fission fragments • The fission fragments are generally in the form of smaller atomic nuclei and neutrons • Large amounts of energy are produced by the fission process
Quick Review **Alpha Particles: 1) Particles release Helium nucleus 2) Change the atomic number by 2 protons **Beta Particles: 1) Quick electron emissions 2) Changes atomic number by 1 **Gamma Particles: 1) Doesn’t change atomic number at all 2) High electromagnetic waves **Isotopes—Different number of neutrons **Fission-splitting of a nucleus **Fusion—2 nuclei combine
