Editing Atom (section)

=== Discovery of the electron ===
In 1897, [[J. J. Thomson]] discovered that [[cathode ray]]s can be deflected by electric and magnetic fields, which meant that cathode rays are not a form of light but made of electrically charged particles, and their charge was negative given the direction the particles were deflected in.<ref>{{cite journal |author=J. J. Thomson |url=http://web.lemoyne.edu/~GIUNTA/thomson1897.html |title=Cathode rays |journal=Philosophical Magazine |volume=44 |issue=269 |pages=293–316 |year=1897}}</ref> He measured these particles to be 1,700 times lighter than [[hydrogen]] (the lightest atom).<ref>In his book ''The Corpuscular Theory of Matter'' (1907), Thomson estimates electrons to be 1/1700 the mass of hydrogen.</ref> He called these new particles ''corpuscles'' but they were later renamed ''[[electron]]s'' since these are the particles that carry electricity.<ref>[http://library.thinkquest.org/C0111709/English/DC-Circuts/mechanism.html "The Mechanism Of Conduction In Metals"] {{Webarchive|url=https://web.archive.org/web/20121025004809/http://library.thinkquest.org/ |date=25 October 2012 }}, Think  Quest.</ref> Thomson also showed that electrons were identical to particles given off by [[Photoelectric effect|photoelectric]] and radioactive materials.<ref name="Thomson">{{cite journal|last=Thomson|first=J.J.|title=On bodies smaller than atoms|journal=The Popular Science Monthly|pages=323–335|date=August 1901|url=https://books.google.com/books?id=3CMDAAAAMBAJ&pg=PA323|access-date=21 June 2009|archive-date=1 December 2016|archive-url=https://web.archive.org/web/20161201152039/https://books.google.com/books?id=3CMDAAAAMBAJ&pg=PA323|url-status=live}}</ref> Thomson explained that an electric current is the passing of electrons from one atom to the next, and when there was no current the electrons embedded themselves in the atoms. This in turn meant that atoms were not indivisible as scientists thought. The atom was composed of electrons whose negative charge was balanced out by some source of positive charge to create an electrically neutral atom. Ions, Thomson explained, must be atoms which have an excess or shortage of electrons.<ref>J. J. Thomson (1907). ''On the Corpuscular Theory of Matter'', p. 26: "The simplest interpretation of these results is that the positive ions are the atoms or groups of atoms of various elements from which one or more corpuscles have been removed [...] while the negative electrified body is one with more corpuscles than the unelectrified one."</ref>