Physics214Week15

Physics214Week15 - This Week Atoms and nuclei What are we...

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This Week Atoms and nuclei What are we made of? The periodic table Why does it stop? How were the elements made? Radioactive decay Useful but can be toxic Discovery of X Rays: Cathode Rays and TV sets Medical imaging Limit your dose 12/09/11 Physics 214 Fall 2011 1
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12/09/11 Physics 214 Fall 2011 2 The basic building blocks The basic building blocks that make up atoms are charge mass Proton 1.6 x 10 -19 1.672 x 10 -27 kg Neutron 0 1.675 x 10 -27 kg Electron -1.6 x 10 -19 9.1 x 10 -31 kg Photon 0 E = hf p = h/λ h = Planck’s constant = 6.626 x 10 -34 J.s
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12/09/11 Physics 214 Fall 2011 3 The nucleus The nucleus was found by Rutherford in scattering charged particles from a gold foil. He observed that occasionally the charged particle was deflected through a large angle indicating it had “hit something hard”
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12/09/11 Physics 214 Fall 2011 4 Atoms Atoms are made up with a central nucleus of protons and neutrons surrounded by a number of electrons equal to the number of protons. The notation we use is 2 He 4 2 is the atomic number = number of protons (and electrons) 4 is the mass number = number of protons + neutrons Note atomic mass is the actual mass of the nucleus in atomic mass units with Carbon set to be 12 units and atomic mass in general is not an integer H 2 O gives the number of atoms required to make a molecule water = 2 Hydrogen plus 1 Oxygen In a nuclear reaction energy, charge, and atomic mass are conserved. Atoms can decay Atoms can join together to form new atoms or molecules Chemistry is determined by the electrons
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12/09/11 Physics 214 Fall 2011 5 Isotopes For a given number of protons there is a nucleus that is most stable for a particular number of neutrons. Isotopes are when for the same number of protons
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This note was uploaded on 12/07/2011 for the course PHYS 214 taught by Professor Staff during the Fall '08 term at Purdue.

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Physics214Week15 - This Week Atoms and nuclei What are we...

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