In the diamond modification of solid carbon each atom is covalently bonded to ex
ID: 622552 • Letter: I
Question
In the diamond modification of solid carbon each atom is covalently bonded to exactly four nearest neighbors that are configured in a tetrahedral pattern around it. In the graphite modification of carbon the carbon atoms form planar sheets that are relatively widely separated from one another. Each carbon atom is bonded to three near neighbors in the plane, and has a weak interaction with atoms in adjacent planes. Diamond is an electrical insulator and is one of the hardest substances known. Interpret these properties in terms of its bonding.Explanation / Answer
Since each carbon atom has four carbon neighbors, its four sp3 hybrid bonds are saturated. All electron states in the bonds are filled, so there can be no net electron motion from bond to bond. The only mechanism available to conduct electricity is the excitation of valence electrons into excited orbitals. However, this requires a significant activation energy and is, consequently, a rare event at all normal temperatures. The conductivity is very low; diamond is an insulator. The hardness of diamond is largely due to the rigidity of its bonding. In order for the carbon to deform its atoms must move with respect to one another. The local distortion of the atom configuration requires some reconfiguration of the valence electron distribution. However, these electrons are in very strong, saturated bonds that are difficult to distort.