Sheppard Software is a great site that offers many different learning games covering a plethora of topics and subject matter. One of my Social Studies Teaching Colleagues uses the sites States and Capitals games to help his classes study for their Geography Tests. One of the neat sections of their site that would be a great connection to your Chemistry lessons would be their Chemistry Games Page.
The Sheppard Software Chemistry Games Page features 8+ games covering the Elements and the Periodic Table. These games vary in levels of difficulty that you can choose. If you are looking for a resource to help your students study the Elements and the Periodic table, or a simply resource to extend your classroom lessons, check out the Chemistry Games page on Sheppard Software.