This document discusses Lewis acid-base theory. It defines a Lewis acid as a substance that can accept an electron pair to form a covalent bond, while a Lewis base is a substance that can donate an electron pair to form a covalent bond. The Lewis definitions include all Brønsted-Lowry acids and bases. According to Lewis, an acid accepts an electron pair during a reaction and a base donates an electron pair.

1. ACID &BASE
THEORIES
Lesson 2: LEWIS
ACIDS AND BASES

2. OBJECTIVES
 Define a Lewis acid and base.
Deduce the Lewis acid and base in a chemical reaction

3. How can one substance, such as
water, be both an acid and a base,
according to the Brønsted-Lowry
definition?
Because water can act as both a
hydrogen-ion donator and a hydrogen-ion
acceptor, it can act as both an acid and a
base according to the Brønsted-Lowry
definition.
Warm up :

4. According to Gilbert Lewis, an acid
accepts a pair of electrons a base
donates a pair of electrons during a
reaction.
• This definition is more general than
those offered by Brønsted and Lowry.
LEWIS ACIDS AND
BASES

5. • A Lewis acid is a substance that can
accept a pair of electrons to form a
covalent bond.
• A Lewis base is a substance that can
donate a pair of electrons to form a
covalent bond.
LEWIS ACIDS AND
BASES
– The Lewis definitions include all the
Brønsted-Lowry acids and bases.

6. Consider the reaction of H+ and OH–.
• The hydrogen ion donates itself to the
hydroxide ion.
– H+ is a Brønsted-Lowry acid, and OH− is a
Brønsted-Lowry base.
LEWIS ACIDS AND
BASES

7. LEWIS ACID/BASE
REACTION

8. Acid-Base Definitions
Type Acid Base
Brønsted-
Lowry
H+ donor H+ acceptor
Lewis
electron-pair
acceptor
electron-pair
donor
This table compares the definitions of acids
and bases.
•The Lewis definition is the broadest.
•It extends to compounds that the Brønsted-Lowry theory does
not classify as acids and bases