If you haven't yet seen The Elements: A Visual Exploration ($13.99, App Store) on the iPad, do yourself a favor and check out this video demo. The Elements is one of a new breed of platform apps that was designed specifically for the iPad. One problem though: it takes 1.75GB of space. 16GB iPad owners may find themselves scrounging for space, I know that I did.
It is impossible to describe in words the experience of seeing and almost feeling over 500 examples of the chemical elements in virtual form, but to give you an idea of the astonishing depth and beauty of the ebook, you can see a preview of all the individual pages from the ebook. Keep in mind that in the real thing, essentially every one of these objects can be spun around a complete circle with the slightest touch of your finger, and can even be seen in stereo 3D using glasses available below.
You can even see over 500 finger-rotatable live 3D objects in true 3D stereo with a $5 pair of prism-type 3D glasses. And don't forget this little easter egg. Man, I wish I had an iPad when I had to learn the periodic table.
It's a mind blower and a must-get. I'd give it six stars if I could.