Lewis Acids & Bases Supplemental

The Lewis acid-base theory extends the definition of an acid and base from [H+] and [OH-].  Lewis' theory used electrons instead of protons.  His theory says that bases are electron donors and acids are electron acceptors.  When a base donates a pair of electrons to an acid, a coordinate covalent bond is formed. In the above video, ChemisNATE illustrates via Lewis structures how electrons are transferred from bases to acids.  You have to remember how to draw Lewis Structures for simple compounds.

In the example below, BF3 is behaving as a Lewis acid.  Ammonia, NH3, is behaving as a Lewis base.  The lone pair of electrons on nitrogen moves to boron and the result is a coordinate covalent bond.