Earlier in this lesson, you were asked to consider the symmetry of a crystal within silica glass. In the ball-and-stick model that was presented, a red ball represented each oxygen atom. These atoms have a slight negative charge. The central white ball represents a silicon atom that has a slight positive charge.



Image by Free-Photos from Pixabay


The fact that the oxygen atoms are negatively charged and the central silicon atom is positively charged means that electrostatic forces apply to this situation. However, the net electrostatic force on each atom is zero.  In other words, the forces are in a state of equilibrium. The angles and distances between the atoms simply describe the overall state of this system when the forces are balanced.

Given the central role played by the electrostatic force, one could say that the shape of this crystal below is a direct consequence of Coulomb's law. The same thinking could apply to almost any crystal!