Quantifying the dative bond: A computational module for bridging the Lewis symbolic-quantum gap at undergraduate level

Abstract

Traditional chemistry education often relies on symbolic representations, such as the Lewis dative arrow, which can lead to significant student misconceptions regarding the physical nature of electron sharing. This paper presents a pedagogical module implemented at the University of Burundi designed to bridge the gap between these abstract symbols and quantum reality. Using the H3N→BH3 adduct as a model system, students performed Density Functional Theory (DFT) calculations and Natural Bond Orbital (NBO) analysis using Gaussian 09. The results allowed students to quantify the interaction through three critical lenses: (i) the Second-Order Perturbation Energy (E2 ), which provided a thermodynamic measure of the nN→pB orbital donation; (ii) Natural Population Analysis (NPA), which revealed a net partial charge transfer (QCT) of 0.34e, contradicting the all-or-nothing perception of electron transfer; and (iii) the Wiberg Bond  Index  (WBI), which offered a numerical value for bond order. By visualizing the overlap of the Nitrogen lone pair with the empty Boron p-orbital, students transitioned from memorizing symbolic arrows to understanding the dynamic delocalization of electron density. This module demonstrates that integrating computational tools into higher education curricula effectively clarifies complex bonding concepts and modernizes the training of future chemists in resource-constrained environments.