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