Hi there,
I would be happy to include an admin panel where one could add new info for any element. Info could be text, HTML, but could also contain images. I suggest having "importance" field too, defined for each new "article" about the element, so that more important stuff about the element is listed above less important stuff. Importance could be a dropdown 1-10, or whatever range you feel would be necessary.
I would try to make the periodic table interactive and fun to use. I'd probably go with HTML 5 canvas, or an SVG. I could make the cells highlight on hover, on clicking the element I could mark them "active", for example by having a border around the active element. Once activated, I would make the page scroll down automatically, until the first article about the clicked element is inside the viewport.
I would have an "X" if the periodic table is not in the viewport (for easy returning to the table), while in cases when it is in the viewport I guess there is no need for the "X", clicking the active element could de-activate it, hiding the section with articles, or loading the new ones if the element was de-activated by clicking/activating another element.
The articles could scroll in a similar way as on the sample website, but that effect heavily relies on fixed backgrounds. To solve this, I could allow uploading background images per element (in admin), and depending on how many are added, use them to create such effect.
Regards,
Julijan