Visualization Types Chart is missing at least one type ...

There's a neat visulization of the various methods of visualizing data. Here is the interactive version, which includes little pop-up examples of each method as you mouseover them. The static graphic is below.  It's all very cool.  Except that they seem to be missing a very important one, or at least a very pertinent one.

Any guesses?

There's no entry for periodic table visualizations! Isn't that weird?

Anyway, visit the page for a good look at each of these.  Maybe save the page for students' reference.