https://itunes.apple.com/us/app/molecules/id284943090

Molecules is an application for viewing three-dimensional renderings of molecules and manipulating them using your fingers. You can rotate the molecules by moving your finger across the display, zoom in or out by using two-finger pinch gestures, or pan the molecule by moving two fingers across the screen at once. These structures can be viewed in both ball-and-stick and spacefilling visualization modes.