Selection Rules of 3D Molecular Structures

The selection rules for predicting and understanding molecular shapes are the following  

Bond pairs and lone pairs around the atom will be distributed in space so as to maximize their distances and minimize thereby the pair-pair repulsion. The preferred molecular shape will depend on the number of pairs that have to distance themselves around a given atom. 

The rules are known in chemistry as the VSEPR rules, where VSEPR is the acronym of valence-shell electron-pair repulsion, and they were devised in 1957 by Gillespie and Nyholm, ] two young scientists—one English, Gillespie, and the other Australian, Nyholm—who were both students of Sir Christopher Ingold, one of the greatest British chemists in the post-Second World War era. 

Let us now apply these rules and predict the shapes of some molecules. As examples, we are going to use simple molecules we have constructed already in Lecture 2. 

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