A Tale of Two Elements: The Lewis Acidity/Basicity Umpolung of Boron and Phosphorus

This lesson delves into Lewis acids and bases in the context of the octet rule for electron-deficient compounds. Here, the concept is discussed, emphasizing the group 13 elements like boron or aluminium. Since group 13 elements possess three valence electrons, they form trivalent compounds with a sextet of electrons and a vacant orbital for the central atom. Consequently, these electron-deficient compounds accept electrons from other species to complete their octet in a chemical reaction. They...

In 1923, G. N. Lewis proposed a generalized definition of acid-base behavior in which acids and bases are identified by their ability to accept or to donate a pair of electrons and form a coordinate covalent bond.
A coordinate covalent bond (or dative bond) occurs when one of the atoms in the bond provides both bonding electrons. For example, a coordinate covalent bond occurs when a water molecule combines with a hydrogen ion to form a hydronium ion. A coordinate covalent bond also results when...

Many covalent molecules have central atoms that do not have eight electrons in their Lewis structures. These molecules fall into three categories:

The VSEPR theory can be used to determine the electron pair geometries and molecular structures as follows:

Dipole Moment of a Molecule

VSEPR Theory for Determination of Electron Pair Geometries