Interactive Periodic Table

Probably the best periodic table on the nets, ptable has it all, advanced colour-coding, links to wikipedia pages on the elements, isotopes, specific proprieties, and (oh!) it's also a periodic table. Check it out!

The universe as rounding error

Image via Wikipedia

I enjoyed this quote: "Nine out of every 10 atoms in the universe are hydrogen, the first element and the major constituent of stars. The other 10 percent of all atoms are helium. That's already 100 percent. The rest of the periodic table, Elements 3 through 118, lithium through ununoctium, barely register on a cosmic scale. The rest of the universe, you and I included, is a rounding error."
                       Sam Kean/  Hydrogen: Where It All Started in Slate

www.periodicvideos.com

The periodic table is a way of representing the 118 elements (one of which, #117 Ununseptium, has never been seen and apparently will decay in a few nanoseconds if it is ever formed). I like this site from the University of Nottingham in England, that links each cell in the periodic table to a charming YouTube video about each one of those elements. The scientist with the wild hair is great.
I linked the video for sodium here. It's a pretty random choice, but this is a typical and quite amusing video.