Ed Pegg Jr writes "Theo Gray, a co-creator of Mathematica, was originally a chemist. Needing a conference table, he created a Periodic Table using a variety of woods." It seems Theo is missing some elements for the table, in case you have any spare europium (in a proper container, of course) lying about. This isn't Theo's first piece of furniture. It looks like he has left a few spots for new elements, and it is nicely modular, in the event an element is found not to exist.