I'm currently rebuilding this from the ground up mostly to replace my handmade animations with CSS transitions. Both the old and new were built with no JS frameworks or libraries and the one you're looking at does well in IE6, to give you an idea of how long ago it was refreshed.
I like this resource for learning about the elements, esp. the drill-down, which makes it fast to go back-and-forth. Also the "Wide" view is cool - I don't remember how long it took me initially to realize that the lanthanide / actinide rows actually belong in the middle of the other ones. :)
This one is much prettier and no ads: <a href="http://www.rsc.org/periodic-table" rel="nofollow">http://www.rsc.org/periodic-table</a>
I just recently discovered the Table of Nuclides [1].<p>[1] <a href="https://en.wikipedia.org/wiki/Table_of_nuclides" rel="nofollow">https://en.wikipedia.org/wiki/Table_of_nuclides</a>
I prefer this more regular style of presenting the periodic table:<p><a href="https://en.wikipedia.org/wiki/Template:Extended_periodic_table_(by_Fricke,_32_columns,_compact)" rel="nofollow">https://en.wikipedia.org/wiki/Template:Extended_periodic_tab...</a><p><a href="https://en.wikipedia.org/wiki/File:Periodic_table_blocks_spdf_(32_column).svg" rel="nofollow">https://en.wikipedia.org/wiki/File:Periodic_table_blocks_spd...</a><p><a href="https://en.wikipedia.org/wiki/File:Periodic_table_(metals%E2%80%93metalloids%E2%80%93nonmetals,_32_columns).png" rel="nofollow">https://en.wikipedia.org/wiki/File:Periodic_table_(metals%E2...</a><p><a href="https://en.wikipedia.org/wiki/File:32-column_periodic_table-a.png" rel="nofollow">https://en.wikipedia.org/wiki/File:32-column_periodic_table-...</a><p>This one is even more different:<p><a href="https://en.wikipedia.org/wiki/Template:Periodic_table_(left_step)" rel="nofollow">https://en.wikipedia.org/wiki/Template:Periodic_table_(left_...</a>
I saw this first back in school in 2013 and was instantly blown away. It was like the perodic table came to life.
Perhaps this is one of the influences that eventually led me to become a software dev