ABSTRACT
The surface layer (selvage layer) of a bulk solid consists of about three or fewer layers of atoms or molecules, a few angstroms at the most [1]. These surface atoms on average have fewer nearest neighbors. Having fewer neighbors raises the energy and hence lowers the stability of those atoms and, consequently, of the surface itself. We know from our earlier discussion of electron shells, nuclear stability, and magic numbers that closed structures are preferred due to their enhanced stability (e.g., the state of minimal energy). In a bulk metal fcc crystal, the optimal coordination number Z for each atom is 12. Anything less than this ideal imparts an inherent instability to the surface (e.g., by way of the dangling bond). Dangling bonds spread gloom over the surface-a state of high anxiety. Dangling bonds must fi nd ways to compensate for the apparent defi - ciencies by whatever chemical or physical means available to them. Please take note that we are only referring to bulk surfaces in this last discussion. If surface atoms do exist in a state of higher energy than fully coordinated volume atoms, we can safely conclude that it must take an investment in energy to create a new surface.
