Nonbonding electrons do matter greatly

lthough they exist ubiquitously in our daily activities, the significance of nonbonding states, such as broken bonds, nonbonding lone pair and unpaired electrons, and antibonding dipoles, are often overlooked in practice. Recent research revealed that the presence of these nonbonding states and the associated energetics dominate the fascinating behavior of low-dimensional functional materials including biologic and organic species. It is my hope that this brief review will help increase the awareness of the importance of these electrons and revive interest in them. At the same time, an emphasis is also placed on the essentiality of interpreting the macroscopic properties of a material from the perspective of bond and nonbond formation, dissociation, relaxation and vibration, and the associated energetics and dynamics of charge repopulation, polarization, densification and localization.