254 lines
11 KiB
HTML
254 lines
11 KiB
HTML
<!DOCTYPE html PUBLIC "-//w3c//dtd html 4.0 transitional//en">
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<html>
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<head>
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<meta http-equiv="Content-Type" content="text/html;
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charset=windows-1252">
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<meta name="GENERATOR" content="Mozilla/4.7 [en] (X11; U; OSF1 V4.0
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alpha) [Netscape]">
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<meta name="Author" content="C. L. Davis">
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<title>Electricity - Structure of Matter - Physics 299</title>
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</head>
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<body style="color: rgb(0, 0, 0); background-color: rgb(255, 255,
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255);" link="#0000ee" alink="#ff0000" vlink="#551a8b">
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<center>
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<h1><img src="ULPhys1.gif" height="50" align="texttop" width="189"></h1>
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</center>
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<center>
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<h1>Structure of Matter</h1>
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</center>
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<center><img src="celticbar.gif" height="22" width="576"> <br>
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<br>
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<font color="#ff0000"><i>"If I have seen further it is by standing
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on the shoulders of giants"</i></font><br>
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Isaac Newton<br>
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</center>
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<img src="netbar.gif" height="40" align="middle" width="100%"> <br>
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<ul>
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<li><img src="ap_cartoon1.gif" alt="cartoon" height="98"
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align="right" width="143"> It is well known today that all
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matter is comprised of atoms. The concept of <a
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href="http://www.visionlearning.com/library/module_viewer.php?mid=49">
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atoms</a> was postulated by the <a
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href="http://www.mlahanas.de/Greeks/Greeks.htm"> ancient
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Greeks</a> , but their existence was not confirmed until a
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little more than 100 years ago. All atoms consist of a
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nucleus made of <b> protons</b> and <b>neutrons</b> around
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which <i> "orbits"</i><img src="atomspin2.gif" alt="atom
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spinning" height="48" align="top" width="48"> one or more <b>electrons</b>.
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</li>
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<br clear="all">
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<br>
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<li>The basic properties of protons, neutrons, electrons and the
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atom as a whole are described in the following table.<br>
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<br>
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<table bgcolor="#ffffcc" border="1" cellpadding="2"
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cellspacing="2" width="100%">
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<tbody>
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<tr>
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<td bgcolor="#ffff00" valign="top">
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<div align="center"><b>Particle</b><br>
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</div>
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</td>
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<td bgcolor="#ffff00" valign="top">
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<div align="center"><b>Electric charge</b><br>
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</div>
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</td>
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<td bgcolor="#ffff00" valign="top">
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<div align="center"><b>Mass</b><br>
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</div>
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</td>
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<td bgcolor="#ffff00" valign="top">
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<div align="center"><b>Approximate Size</b><br>
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</div>
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</td>
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</tr>
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<tr>
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<td valign="top">
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<div align="center">electron (e<sup>-</sup>)<br>
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</div>
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</td>
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<td valign="top">
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<div align="center">- 1.6 x 10<sup>-19</sup> C<br>
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</div>
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</td>
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<td valign="top">
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<div align="center">9.1 x 10<sup>-31</sup> kg<br>
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</div>
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</td>
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<td valign="top">
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<div align="center"> < 10<sup>-18</sup> m<br>
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</div>
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</td>
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</tr>
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<tr>
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<td valign="top">
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<div align="center">proton (p)<br>
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</div>
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</td>
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<td valign="top">
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<div align="center">+ 1.6 x 10<sup>-19</sup> C<br>
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</div>
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</td>
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<td valign="top">
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<div align="center">1.6 x 10<sup>-27</sup> kg<br>
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</div>
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</td>
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<td valign="top">
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<div align="center">10<sup>-15</sup> m<br>
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</div>
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</td>
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</tr>
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<tr>
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<td valign="top">
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<div align="center">neutron (n)<br>
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</div>
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</td>
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<td valign="top">
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<div align="center">0 <br>
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</div>
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</td>
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<td valign="top">
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<div align="center">1.6 x 10<sup>-27</sup> kg<br>
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</div>
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</td>
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<td valign="top">
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<div align="center">10<sup>-15</sup> m<br>
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</div>
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</td>
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</tr>
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<tr>
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<td valign="top">
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<div align="center">Atom<br>
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</div>
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</td>
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<td valign="top">
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<div align="center">0 (neutral)<br>
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</div>
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</td>
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<td valign="top">
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<div align="center">(N<sub>p</sub> + N<sub>n</sub>) x
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1.6 x 10<sup> -27</sup> kg<br>
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</div>
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</td>
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<td valign="top">
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<div align="center">10<sup>-10</sup> m<br>
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</div>
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</td>
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</tr>
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</tbody>
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</table>
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<br>
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where N<sub>p</sub>, N<sub>n</sub> are the number of protons and
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neutrons, respectively, in the nucleus of the atom.</li>
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</ul>
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<ul>
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<br>
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<img src="ap_scale.jpg" alt="atomic structure" height="340"
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align="right" width="250">
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<li>Other important properties:<br>
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<ul>
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<br>
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<li>Mass of proton (m<sub>p</sub>) is approximately 2000
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times the mass of the electron (m<sub>e</sub>)</li>
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<br>
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<li>More than 99% of the volume of an atom is empty space.
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If the nucleus of the Hydrogen atom was one inch in
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diameter the orbit of the electron would have a radius of
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<EFBFBD> mile.</li>
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<br>
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<li>Current experiments indicate that the electron has no
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structure, it is a true <i>point</i> particle.</li>
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<br>
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<li>Protons and neutrons are each comprised of <a
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href="http://www.fact-index.com/q/qu/quark.html"> quarks.</a>
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With the same experimental limit as the electrons,
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quarks also have no sub-structure.</li>
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<br>
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<li>The wavelength of visible light is of order 5 x 10<sup>-7</sup>
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m. Atoms are typically more than 1000 times smaller
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than this wavelength. <br>
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</li>
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</ul>
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</li>
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<br clear="all">
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<li> The properties of the different elements in nature, e.g.
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Hydrogen, Sodium, Uranium etc. are defined by their <i>"atomic
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structure"</i>. These elements can be arranged in a form
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known as the <i><a href="http://www.webelements.com/">
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"periodic table"</a> </i> which illustrates the
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similarities and differences between them. <a
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href="http://en.wikipedia.org/wiki/Dmitri_Mendeleev">Dmitri
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Mendeleev</a> <img src="mendeleev.gif" alt="mendeleev"
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height="124" align="middle" width="90"> is generally
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considered the creator of the modern <a
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href="http://periodic.lanl.gov/index.html"> periodic table</a>.<br>
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Nottingham University has created the <a
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href="http://www.periodicvideos.com/#">Periodic Table of
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Videos</a>, which features a short video clip describing the
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properties, history, production etc of each element.</li>
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</ul>
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<ul>
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<li>Starting with the <a href="http://periodic.lanl.gov/1.shtml">
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Hydrogen</a> atom, which consists of a single proton nucleus
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and a single electron, different elements can be created by
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adding additional protons to the nucleus while at the same time
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adding the same number of electrons to keep the atom neutral.
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For light elements (excluding Hydrogen) the number of
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neutrons in the nucleus is equal to the number of protons; for
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heavier elements a neutron excess develops. For example
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the most common <a href="http://periodic.lanl.gov/82.shtml">
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Lead</a> atom comprises 82 protons and 126 neutrons. The
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heaviest naturally occuring element is <a
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href="http://periodic.lanl.gov/92.shtml"> Uranium</a> , having
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92 protons and 146 neutrons. Certain elements with more
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protons can be created but undergo radioactive decay with a
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lifetime shorter than that of the earth.<br>
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<div align="center"><img src="ap_atomexam.gif" alt="atomic
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examples" height="149" align="middle" width="372"></div>
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</li>
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</ul>
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<br>
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<ul>
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</ul>
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<ul>
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<li><big><big style="font-weight: bold; color: rgb(255, 0, 0);"><font
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color="#000000">For this course, the it is important to
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realize that the negatively charged electrons are held in
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"orbit" around the positively charged nucleus by the
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electric force of attraction. In fact all atomic and
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molecular forces of any significance are electrical (or
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electromagnetic) in nature. It could be said that
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all of Chemistry is due to the electromagnetic
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force. In fact virtually all everyday physical
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phenomena are electromagnetic in nature, friction,
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thermodynamics, elasticity etc etc. Only those
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phenomena involving very large masses (where the
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gravitational force becomes significant) and certain very
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small scale processes (e.g. radioactive decay, fission,
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fusion) are not primarily electromagnetic in nature.</font>
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Understanding electricity and magnetism - electromagnetism
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- is critical to our understanding of nature.</big></big><span
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style="color: rgb(255, 0, 0);"> </span> <br>
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</li>
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</ul>
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<img src="netbar.gif" height="40" width="100%">
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<center><span style="font-style: italic; color: rgb(255, 0, 0);">A
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neutron walks into a bar. "I'd like a beer" he says. The
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bartender promptly serves up a beer. "How much will that be?"
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asks the neutron. "For you?" replies the bartender, "no charge"<br>
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<br>
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</span><img src="celticbar.gif" height="22" width="576"><br>
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<p><i>Dr. C. L. Davis</i><br>
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<i>Physics Department</i><br>
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<i>University of Louisville</i><br>
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<i>email</i>: <a href="mailto:c.l.davis@louisville.edu">c.l.davis@louisville.edu</a>
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<br>
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</p>
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<p><img src="header-index.gif" height="51" width="92"> </p>
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</center>
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<p><br>
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</p>
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</body>
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</html>
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