STRUCTURE AND PHASES OF MATTER UNIT REVIEW By Mrs. Susan Dennison 2012-13.
Unit 5 The Structure of Matter
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Transcript of Unit 5 The Structure of Matter
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Unit 5 The Structure of Matter
Chapter 16 The Atom
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16C – The Nuclear Atom• Objectives:
– Define radioactivity and identify important kinds of nuclear radiation
– Describe the various processes of nuclear decay and how each affects the atom
– Use nuclear decay equations to illustrate each kind of decay process
– Discuss one application of nuclear decay t hat helps save lives
– Compare and contrast nuclear fission and fusion, including the conditions under which each occurs
– Discuss the difficulties of developing electrical generation using fusion energy
• Assignments: Outline, Worksheet and Section Review page 405
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Nuclear Radiation• Antoine Henri Becquerel
– French physicist who discovered nuclear radiation and radioactivity
– Won Nobel Prize in Physics• Too many or too few neutrons in an atom leads
to less stability• Nuclear Chemistry
– The study of changes that occur in the atomic nuclei– Began by the accidental discovery of radioactivity
• The emission of nuclear radiation– Rays and particle emitted by unstable nuclei
• Experiments led to the discovery of alpha particles, beta particles, and gamma rays– symbolized by the Greek letters
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Nuclear Decay• Larger nucleus = excess energy• Gamma Decay– No change in the atom except for
reducing the amount of energy in its nucleus
– Can be very damaging to organic molecules found in living things
– Molecules that absorb gamma rays can be destroyed as the energy disrupts bond between atoms
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Alpha Decay• More significant then gamma• Loses an alpha particle, equal to helium
– Atom’s nucleus loses two protons and two neutrons, reducing its atomic number by 2 and its mass number by 4
• Because its atomic number has changed, the atom is now an isotope of a DIFFERENT element
• Once the alpha particle hits something it gains electrons and becomes a normal helium atom; however it tends to interact with other atoms very easily, damaging chemical bonds as it rips electrons away from other atoms and molecules
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Beta Decay• Ratio of protons and neutrons is too
large to be stable• A neutron changes to a proton• Emits a beta particle, a high energy
electron• The mass number stays the same• The atomic number increases by one
changing the atom into an isotope of another element
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Decay Equations
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What Can Stop Radiation?
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Nuclear Bombardment Reactions
• Happens when a nucleus is struck by a high energy particle or another nucleus
• Different than nuclear decay because bombardment reactions release millions of times more energy and many more particles than alpha or beta decay
• Almost always artificially induced in special nuclear reactions and particle accelerators
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Nuclear Fission• Occurs when a large, unstable nucleus splits into
smaller, more stable nuclei, releasing energy• Forced to occur artificially in a nuclear reactor• Can also occur spontaneously, although rare• As neutrons are released they are absorbed by
other nuclei which also fission releasing more free neutrons causing a chain reaction
• In a controlled nuclear chain reaction an immense amount of energy can be release to do useful work
• Fission bombs are better known as atomic bombs or nuclear bombs
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Nuclear Fusion
• The opposite of fission• Smashing smaller nuclei together to
form a large one• Produces even more energy than
fission• Fusion bombs, better known as
hydrogen bombs or thermonuclear bombs