The general assumption is that at the quantum level, atoms lack a defined shape beyond their nucleus, and thus can only be represented by a probability-based "electron cloud." In point of fact, there is overwhelming evidence that (1) each element in the periodic table has a permanent, defined shape; (2) that the variations in atomic design are standardized from one element to the next; and (3) that the overall shape of an element controls the majority of the atom's properties. Instead of trying to fill this post with too much detail. I will just point you to the website created for purposes of describing and displaying 3D models of various elements. The website address is: smacscience [dot] com There are also links to a YouTube channel and a Flickr photostream accessible from the website homepage. Thus far, only about 40 of the elements have been fully modeled, though that is more than enough to demonstrate the standardized design of the elements, and the way in which their shape controls their properties. The evidence for standardized atomic structure is overwhelming in that the patterns of variations in shape created by a standardized design correspond directly to variations in many of the properties of the elements; things such as density, hardness, electrical conduction, catalysis and state of matter at room temperature. In other words, the models created from the standardized design predict, with 100% accuracy, the aforementioned classes of elemental properties. As such, coincidence is simply not a possibility.