ABSTRACT
The properties of a solid and the way its atoms are arranged in three-dimensional are determined primarily by the nature and directionality of the bonds holding the atoms together. In principle, the procedure for determining the shape of an atomic or molecular orbital is quite simple and involves solving Schrodinger’s equation—with the appropriate boundary conditions—from which one obtains the all-important electronic wave function. The solution for a polyelectronic atom is similar to that of the hydrogen atom except that the former is inexact and is much more difficult to obtain. Ionic compounds generally form between quite active metallic elements and active nonmetals. Ionic bonds are omnidirectional. Ionic compounds are typically hard and brittle and are poor electrical and thermal conductors. One of the more successful theories developed to explain a wide variety of electrical and optical properties in solids is the band theory of solids.
