Application of the Covalent Bond Classification Method for the Teaching of Inorganic Chemistry

The Covalent Bond Classification (CBC) method provides a means to classify covalent molecules according to the number and types of bonds that surround an atom of interest. This approach is based on an elementary molecular orbital analysis of the bonding involving the central atom (M), with the various interactions being classified according to the number of electrons that each neutral ligand contributes to the bonding orbital. Thus, with respect to the atom of interest (M), the ligand can contribute either two (L), one (X), or zero (Z) electrons to a bonding orbital. A normal covalent bond is represented as M–X, whereas dative covalent bonds are represented as either M←L or M→Z, according to whether the ligand is the donor (L) or acceptor (Z). A molecule is classified as [ML l X x Z z ] according to the number of L, X, and Z ligand functions that surround M. Not only does the [ML l X x Z z ] designation provide a formal classification of a molecule, but it also indicates the electron configuration, the valence, and the number of nonbonding electrons on M. As such, the classification allows a student to understand relationships between molecules, thereby increasing their ability to conceptualize and learn the chemistry of the elements.