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Chapter 25 Winter 2011

Chapter 25 Winter 2011 - Chapter 25 Nuclear Processes Quiz...

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Chapter 25 Nuclear Processes Quiz: Did you read Chapter 25 for today? a) Yes b) No Earth But first… From the BBC: square4 Remember van der Waals or dispersion forces? Apparently they are the most important force in holding geckos to walls. Weird Interactions square4 Recall there are four in the universe: Gravity Electromagnetic Nuclear Weak Nuclear Strong square4 We’ve studied the first two. Now we will learn about the two nuclear ones.
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Nucleons square4 Both protons or neutrons are called nucleons. square4 Protons feel both the attractive strong nuclear force and the repulsive electromagnetic force. square4 Neutrons only feel the attractive strong nuclear force. Force equations square4 Gravity: F = GMm/d 2 square4 Electromagnetic: F = kQq/d 2 square4 Strong Nuclear: F = ?? We do not yet have a single equation for the Strong Nuclear force! But we know it is VERY short range. d M m d Q q d N n square4 Weak nuclear: F = ?? Theories called Grand Unified Theories (GUTs) say that it is really a manifestation of the electromagnetic force… Still more work to be done… Atomic and Nuclear Models square4 Electron energy levels have been measured experimentally Emission spectra. square4 Patterns were recognized. This led to the Bohr model square4 Nuclear energy levels have been measured experimentally. Gamma rays square4 Scientists are still looking Atomic Nuclear square4 We have a working Quantum Mechanical model. square4 Electron energies can now be calculated exactly using electric force laws and equations for wave behavior. for patterns. square4 We have pieces of a quantum mechanical model. There are still some holes. square4 We cannot yet calculate exact values for nucleon energies. Atoms and Isotopes square4 Atomic number = number of protons. This is what makes an element unique. square4 Mass number = number of nucleons. Different isotopes have different numbers of neutrons. 16 O 18 O 17 O neutron proton 8 8 8
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Mass Number square4 The mass number on the periodic table is an average over all isotopes.
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