WebElements™ Periodic Table by Mark Winter, Department of Chemistry, University of Sheffield, England:

• Professional Edition: WebElements aims to be a high quality source of chemistry information on the WWW relating to the periodic table. Coverage is such that professional scientists and students at school interested in chemistry and other sciences will all find something useful.
• Scholar Edition: The WebElements scholar edition aims to be a high quality source of information on the WWW about the periodic table for students. You will find many pictures showing element structures and periodic properties. Note that elements 113, 115, and 117 are not known, but are included in the table to show their expected positions. Elements 114, 116, and 118 have only been reported recently.

Periodic Table from Computer Science at UBC