Atom-Bond Connectivity Index
Mathematical chemistry is the area of research engaged in novel applications of mathematics to chemistry; it concerns itself principally with the mathematical modeling of chemical phenomena. Chemical graphs, particularly molecular graphs, are models of molecules in which atoms are represented by vertices and chemical bonds by edges of a graph. Physico-chemical or biological properties of molecules can be predicted by using the information encoded in the molecular graphs, eventually translated in the adjacency or connectivity matrix associated to these graphs. The bounds of a topological index are important information of a molecular graph in the sense that they establish the approximate range of the index in terms of molecular structural parameters. In order to reduce the arbitrariness in the production of novel topological indices, several criteria are put forward that such a molecular structure descriptor should be required to satisfy.