Acids, Bases And Salts - Theories

Lewis or Electronic theory of acids and bases

According to Lewis theory, an acid is any molecule, ion or atom which can accept a pair of electron to form a co-ordinate covalent bond. Example: H⁺, BF₃.
Base is a substance which can donate a pair of electrons to form a co-ordinate covalent bond. Example: NH₃, H₂O, Cl^- etc.
An acid is a electron-pair acceptor and a base is electron-pair donor. Any substance which has a lone pair of electron can act as a base and acid is a substance with empty orbital.
A reaction between an acid and a base which result in the formation of co-ordinate covalent bond is called neutralisation reaction.

Types of Lewis acids :
A)Cation of d-block elements.
    Example: Cu⁺², Fe⁺², Ag+ etc.
B)Compounds whose central atom has incomplete octet.
    Example: BF₃, BCl₃, AlCl₃ etc.
C)Compounds in which central atom has available d-orbitals and may expand its octet.
    Example: SiF₄, SnCl₄, SF₄.
D)Molecules having multiple bonds between atoms of different electro negativities.
    Example: SO₂, CO₂, NO₂ etc.

Types of Lewis bases:
A)All anions
Example: Cl^-, OH^-, CN^-, NH₂^- etc.
B)Molecules with one or more lone pair of electrons.
    Example: H₂O, NH₃, R-OH, R-NH₂
C)Molecules with multiple bonds
Example:HC  \( \equiv \) CH; H2C \( \equiv \) CH2

Examples of neutralisation reaction:
A)  

B) 

C)