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LEWIS ACID-BASE CONCEPT

According to Lewis acid base theory- acids are electron pair acceptor (electron deficient) and bases are electron pair donor and the combination of Lewis acid and Lewis base occur through coordinate bond formation.
For example
Other examples of Lewis acid-base neutralisation.
LEWIS ACIDS:
(1) Cations are act as Lewis acids example, H+ , Ag+ , Cu+2 , Na+ , Fe+2 , Hg+2  etc.
(2) electron deficient compounds are act as lewise acids for example , BF3 ,ACl3 ,BCl3 ,FeCl3 etc
(3) compounds with available vacant d orbital act as Lewis acids for example , SiCl4 ,PCl5 , SOF4 ,etc
(4) compounds containing multiple bonds for example  CO2.
LEWIS BASES:
(1) Anions are act as Lewis base H- ,CH3- ,NH2- , OH- , X- etc.
     All the anions are not Lewis base for example (PCl5)
(2) Molecules having lone pairs act as Lewis base example NH3 ,H2O , R-OH ,R-O-R , etc
(3) compounds with non polar multiples bond  are also act as Lewis base, example C2H4 , C2H2    (Ligand in coordination compounds)
MERITS OF LEWIS CONCEPT: 
(1) The acid/base nature of substance may also defined without any solvent.
(2) It is highly useful to explain coordination compounds in which central metal atom into behave as Lewis acid and ligands behave as Lewis base.
(3) the acid having greater tendency to accept lone pair bare stronger acid and base have greater tendency to donate lone pair are stronger base.
DEMERITES OF LEWIS CONCEPT:
(1) It is extremaly generalized Concept , almost all the compounds either become acid or base  by this Concept.

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