The term Lewis acid refers to a definition of acid published by Gilbert N. Lewis in 1923, specifically: An acid substance is one which can employ an electron lone pair from another molecule in completing the stable group of one of its own atoms.[1] Thus, H+ is a Lewis acid, since it can accept a lone pair, completing its stable form, which requires two electrons. The modern-day definition of Lewis acid, as given by IUPAC is a molecular entity (and the corresponding chemical species) that is an electron-pair acceptor and therefore able to react with a Lewis base to form a Lewis adduct, by sharing the electron pair furnished by the Lewis base.[2] This definition is both more general and more specific—the electron pair need not be a lone pair (it could be the pair of electrons in a p bond, for example), but the reaction should give an adduct (and not just be a displacement reaction). Crystal field theory (CFT) is a model that describes the breaking of degeneracies of electronic orbital states, usually d or f orbitals, due to a static electric field produced by a surrounding charge distribution (anion neighbors). This theory has been used to describe various spectroscopies of transition metal coordination complexes, in particular optical spectra (colours). CFT successfully accounts for some magnetic properties, colours, hydration enthalpies, and spinel structures of transition metal complexes, but it does not attempt to describe bonding. CFT was developed by physicists Hans Bethe and John Hasbrouck van Vleck[1] in the 1930s. CFT was subsequently combined with molecular orbital theory to form the more realistic and complex ligand field theory (LFT), which delivers insight into the process of chemical bonding in transition metal complexes. In chemistry, valence bond (VB) theory is one of two basic theories, along with molecular orbital (MO) theory, that were developed to use the methods of quantum mechanics to explain chemical bonding. It focuses on how the atomic orbitals of the dissociated atoms combine to give individual chemical bonds when a molecule is formed. In contrast, molecular orbital theory has orbitals that cover the whole molecule. Solution The term Lewis acid refers to a definition of acid published by Gilbert N. Lewis in 1923, specifically: An acid substance is one which can employ an electron lone pair from another molecule in completing the stable group of one of its own atoms.[1] Thus, H+ is a Lewis acid, since it can accept a lone pair, completing its stable form, which requires two electrons. The modern-day definition of Lewis acid, as given by IUPAC is a molecular entity (and the corresponding chemical species) that is an electron-pair acceptor and therefore able to react with a Lewis base to form a Lewis adduct, by sharing the electron pair furnished by the Lewis base.[2] This definition is both more general and more specific—the electron pair need not be a lone pair (it could be the pair of electrons in a p bond, for example.

1. The term Lewis acid refers to a definition of acid published by Gilbert N. Lewis in
1923, specifically: An acid substance is one which can employ an electron lone pair from another
molecule in completing the stable group of one of its own atoms.[1] Thus, H+ is a Lewis acid,
since it can accept a lone pair, completing its stable form, which requires two electrons. The
modern-day definition of Lewis acid, as given by IUPAC is a molecular entity (and the
corresponding chemical species) that is an electron-pair acceptor and therefore able to react with
a Lewis base to form a Lewis adduct, by sharing the electron pair furnished by the Lewis
base.[2] This definition is both more general and more specific—the electron pair need not be a
lone pair (it could be the pair of electrons in a p bond, for example), but the reaction should give
an adduct (and not just be a displacement reaction). Crystal field theory (CFT) is a model that
describes the breaking of degeneracies of electronic orbital states, usually d or f orbitals, due to a
static electric field produced by a surrounding charge distribution (anion neighbors). This theory
has been used to describe various spectroscopies of transition metal coordination complexes, in
particular optical spectra (colours). CFT successfully accounts for some magnetic properties,
colours, hydration enthalpies, and spinel structures of transition metal complexes, but it does not
attempt to describe bonding. CFT was developed by physicists Hans Bethe and John Hasbrouck
van Vleck[1] in the 1930s. CFT was subsequently combined with molecular orbital theory to
form the more realistic and complex ligand field theory (LFT), which delivers insight into the
process of chemical bonding in transition metal complexes. In chemistry, valence bond (VB)
theory is one of two basic theories, along with molecular orbital (MO) theory, that were
developed to use the methods of quantum mechanics to explain chemical bonding. It focuses on
how the atomic orbitals of the dissociated atoms combine to give individual chemical bonds
when a molecule is formed. In contrast, molecular orbital theory has orbitals that cover the whole
molecule.
Solution
The term Lewis acid refers to a definition of acid published by Gilbert N. Lewis in
1923, specifically: An acid substance is one which can employ an electron lone pair from another
molecule in completing the stable group of one of its own atoms.[1] Thus, H+ is a Lewis acid,
since it can accept a lone pair, completing its stable form, which requires two electrons. The
modern-day definition of Lewis acid, as given by IUPAC is a molecular entity (and the
corresponding chemical species) that is an electron-pair acceptor and therefore able to react with
a Lewis base to form a Lewis adduct, by sharing the electron pair furnished by the Lewis
base.[2] This definition is both more general and more specific—the electron pair need not be a
lone pair (it could be the pair of electrons in a p bond, for example), but the reaction should give
an adduct (and not just be a displacement reaction). Crystal field theory (CFT) is a model that

2. describes the breaking of degeneracies of electronic orbital states, usually d or f orbitals, due to a
static electric field produced by a surrounding charge distribution (anion neighbors). This theory
has been used to describe various spectroscopies of transition metal coordination complexes, in
particular optical spectra (colours). CFT successfully accounts for some magnetic properties,
colours, hydration enthalpies, and spinel structures of transition metal complexes, but it does not
attempt to describe bonding. CFT was developed by physicists Hans Bethe and John Hasbrouck
van Vleck[1] in the 1930s. CFT was subsequently combined with molecular orbital theory to
form the more realistic and complex ligand field theory (LFT), which delivers insight into the
process of chemical bonding in transition metal complexes. In chemistry, valence bond (VB)
theory is one of two basic theories, along with molecular orbital (MO) theory, that were
developed to use the methods of quantum mechanics to explain chemical bonding. It focuses on
how the atomic orbitals of the dissociated atoms combine to give individual chemical bonds
when a molecule is formed. In contrast, molecular orbital theory has orbitals that cover the whole
molecule.