What are the classifications of a Lewis acid and a Lewis base?Lewis acid and lewis base

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bandmanjoe eNotes educator| Certified Educator

The definition of a Lewis acid is a substance that is an electron pair acceptor.  This would include most, if not all, metal ions, as they generally are in need of electrons to balance the positive charge  they have from the proton-electron imbalance of ion status.  For example, hydrogen ions (H+) quickly accept an electron pair from a sulfate ion (SO4-2) to form H2SO4, sulfuric acid.  The definition of a Lewis base would be any substance that is an electron pair donor.  In the example mentioned above, the sulfate ion (SO4-2), donates two electrons to a pair of hydrogen ions (H+) in the formation of H2SO4, sulfuric acid.  This satisfies the ionic imbalance of the sulfate ion, which has a -2 charge.  It should be noted that most substances are classified as Bronsted-Lowry acids and bases, where an acid is considered a substance that is a proton donor (H+) and a base is a proton acceptor (OH-).

sanjeetmanna eNotes educator| Certified Educator

Lewis acids→An electron pair acceptor


Lewis base→An electron pair donor

Example→NH3, OH-

The reaction of a lewis acid and lewis base will lead to the formation of coordinate covalent bond, lewis base donates its electron pair to lewis acid

Lewis acids are electrophillic so all the cations are lewis acids since they are ready to accept the electron, along with the incomplete octet rule molecule can form lewis acids...

Where as...

Lewis bases are Nucleophillic they are ready to donte electrons...

Example→ OH-, CN- etc.,

chaobas | Student

According to Lewis theory, an acid is an electron pair acceptor while a base is an electron pair donor.Lewis Acids are Electrophilic meaning that they are electron attracting. Various species can act as lewis acids. All cations are lewis acids since they are able to accept electrons. The best example are Cu2+, Fe2+, Fe3+ . Even an atom, ion, or molecule with an incomplete octet of electrons can act as an lewis acid. Like BF3, AlF3 Moreover Molecules where the central atom can have more than 8 valence shell electrons can be electron acceptors are also lewis acid like SiBr4, SiF4


Lewis Bases donatean electron pair. Lewis Bases are Nucleophilic meaning that they “attack” a positive charge with their lone pair. Like lewis acid, an atom, ion, or molecule with a lone-pair of electrons can thus be a lewis base like OH-, CN-, CH3COO-

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