Carbon

Here's an animation of a carbon atom

Also, look at this short slideshow which explains the unique properties of the carbon atom
(If you don't understand totally, that is all right -- the main thing to understand is that carbon bonds with other elements in an unusual way -- it can form chains, rings, double and triple bonds -- in fact, very complex structures that are necessary for life).

Review

Try this Balancing Quiz
(choose "easy")
Try this Element Matching Game