molecules Review Chemical Bonding: The Journey from Miniature Hooks to Density Functional Theory Edwin C. Constable * and Catherine E. Housecroft Department of Chemistry, University of Basel, BPR 1096, Mattenstrasse 24a, CH-4058 Basel, Switzerland;
[email protected] * Correspondence:
[email protected]; Tel.: +41-61-207-1001 Academic Editor: Antonio J. Mota Received: 10 May 2020; Accepted: 3 June 2020; Published: 5 June 2020 Abstract: Our modern understanding of chemistry is predicated upon bonding interactions between atoms and ions resulting in the assembly of all of the forms of matter that we encounter in our daily life. It was not always so. This review article traces the development of our understanding of bonding from prehistory, through the debates in the 19th century C.E. bearing on valence, to modern quantum chemical models and beyond. Keywords: bonding; valency; affinity, structure; history of science 1. Introduction Bonding is what separates chemistry from physics. If the understanding of atoms and their component particles belongs primarily to the realm of physics, then chemistry is concerned with the aggregation of atoms into chemical entities held together by bonds. If science is a language, and atoms are the letters, bonding is the mechanism by which the letters are combined into words. The International Union of Pure and Applied Chemistry (IUPAC) states that “there is a chemical bond between two atoms or groups of atoms in the case that the forces acting between them are such as to lead to the formation of an aggregate with sufficient stability to make it convenient for the chemist to consider it as an independent ‘molecular species’” [1].