Page 8 - 10-Chem-10 Acid, Bases and Salts

10. Acid, Bases and Salts eLearn.Punjab

(ii) Simple cations can act as Lewis acids. All cations act as Lewis acids since they are
deficient in electrons. However, cations such as Na+, K+, Ca2+ ions, etc., have a very little
tendency to accept electrons. While the cations like H+, Ag+ ions, etc., have a greater
electron accepting tendency therefore, act as Lewis acids.

Lewis bases. According to Lewis concept, the following species can act as Lewis bases:

(i) Neutral species having at least one lone pair of electrons. For example, ammonia,
amines, alcohols etc. act as Lewis bases because they contain a lone pair of electrons:

(ii) Negatively charged species or anions. For example,
chloride, cyanide, hydroxide ions, etc., act as Lewis bases:

Summary of the Concepts.

Concept Acid Base Product
give H+ gives OH salt + H2O
Arrhenius donate H+ accepts H+ conjugate acid base
Bronsted-Lowry electron pair electron pair
acceptor pair
Lewis donor
adduct

It may be noted that all Bronsted bases are also Lewis
bases but all Bronsted acids are not Lewis acids. According to
Bronsted concept, a base is a substance which can accept a proton,
while according to Lewis concept, a base is a substance which can
donate a pair of electrons. Lewis bases generally contain one or more
lone pair of electrons and therefore, they can also accept a proton
(Bronsted base). Thus, all Lewis bases are also Bronsted bases. On
the other hand, Bronsted acids are those which can give a proton. For
example, HCI, H2 SO4 are not capable of accepting a pair of electrons.
Hence, all Bronsted acids are not Lewis acids.

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