Chemestry I - Elements

Periodic Table of the Elements - Los Alamos National Labs
http://periodic.lanl.gov/

Webelements
http://www.webElements.com/

It's Elemental - Jefferson Lab
http://education.jlab.org/itselemental/

EniG. Periodic Table of the Elements
http://www.periodni.com/

Chemical Elements
http://www.chemicalelements.com/

Online Encyclopedias

Search in Worldbook Online -Advanced  in our Reference selections. Search for "Atom"  (without quotations) and then select Atom again and scrool down to the "Development of the atomic theory" option.

Search in Encyclopedia Britannica Online under Atom. Select the top left option titled "Atom" under the high school selections. Then, on the left, you will see table of contents options including "Development of atomic theory."

Databases

Facts on File Science Online

Science Reference Center