Arrhenius Acids and Bases
Bronsted-Lowry Acids and Bases
Lewis Acids and Bases
Ka and Kb of compounds
Weak Acid-Base Equilibria
Ionic Salts of Weak Acids and Bases
Lewis Acids and Bases

Concept #1: A Lewis Acid is an electron deficient species that readily accepts a lone pair. 

Concept #2: A Lewis Base is an electron rich species that readily donates a lone pair. 

Example #1: Identify the Lewis acid and base in the following reaction.

SO2    +  H2O    ⇌   H2SO3