The entries are neither exhaustive in scope nor definitional in quality. A small fraction of the entries define terms introduced in the present work. Some words in the main text are marked in the same way. A reaction that removes an atom from a structure. A neutral Lewis acid and a neutral Lewis base can commonly form a dipolar bond .
Distinct states correspond to minima of a potential energy surface in a configuration space .
Acyclic Not cyclic . AFM An atomic force microscope . A negatively charged ion . Aromatic A term used to describe cyclic pi-bonded structures of special stability. In recent popular usage, any nanomachine , usually assumed to offer magical, universal capabilities in an atom-sized package.