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Lewis acid-base theory
Lewis acid-base theory
Very different from Brønsted-Lowrey
acid-base.
Lewis acid-base theory
Very different from Brønsted-Lowrey
acid-base.
Not dependent on protons
or pH.
Lewis acid-base theory
An acid is a lone-pair acceptor.
Definitions:
Lewis acid-base theory
An acid is a lone-pair acceptor.
H+ no electrons – by accepting 2 electrons it attains noble gas configuration.
Definitions:
Lewis acid-base theory
An acid is a lone-pair acceptor.
H+ no electrons – by accepting 2 electrons it attains noble gas configuration.
BF3 electron deficient compound - B needs 2 electrons for noble gas configuration.
B Group III 3 valence electrons
B Group III 3 valence electrons
F Group VII 7 valence electrons
B Group III 3 valence electrons
F Group VII 7 valence electrons
6 electrons for boron rather than 8
Lewis Acid
Lewis acid-base theory
Lewis base: lone-pair donorDefinitions:
Lewis acid-base theory
Lewis base: lone-pair donor
NH3 N has lone pair
Definitions:
Group V
Group I
Lewis Base
Lewis acid-base theory
Lewis base: lone-pair donor
NH3 - N has lone pair
H2O - O has 2 lone pairs
Lewis acid-base theory
H3N : + BF3 H3N : BF3
Lewis acid-base theory
H3N : + BF3 H3N : BF3
Lewis base
Lewis acid-base theory
H3N : + BF3 H3N : BF3
Lewis base Lewis acid
Lewis acid-base theory
H3N : + BF3 H3N : BF3
Lewis base Lewis acid
Both electrons in thisbond come from nitrogen.
Lewis acid-base theory
H3N : + BF3 H3N : BF3
Lewis base Lewis acid
Coordinate covalent bond
(CH3)3N BCl3
(CH3)3N : + BCl3 (CH3)3N : BCl3
(CH3)3N BCl3
(CH3)3N : + BCl3 (CH3)3N : BCl3
This compound may be referred to as an adduct.
CH3COOH(aq) + NH3(aq)
NH4+
(aq) + CH3COO-(aq)
CH3COOH(aq) + NH3(aq)
NH4+
(aq) + CH3COO-(aq)
NH3 Lewis base
CH3COOH(aq) + NH3(aq)
NH4+
(aq) + CH3COO-(aq)
NH3 Lewis base
CH3COOH is not a Lewis acid.
H+ + NH3(aq)
NH4+
(aq) + CH3COO-(aq)
NH3 Lewis base
CH3COOH is not a Lewis acid.
CH3COOH(aq) + H2O H3O+ + CH3COO-
H+ + NH3(aq)
NH4+
(aq) + CH3COO-(aq)
NH3 Lewis base
CH3COOH is not a Lewis acid.
CH3COOH(aq) + H2O H3O+ + CH3COO-
H3O+ H+ + H2O
CH3COOH(aq) + NH3(aq)
NH4+
(aq) + CH3COO-(aq)
NH3 Lewis base
CH3COOH is not a Lewis acid.
H+ is the Lewis acid.
Al(OC2H5)3
Al(OC2H5)3
Tri-ethoxy aluminum
Al(OC2H5)3
Al is Group III - electron deficient like BF3.
Al(OC2H5)3
Al is Group III - electron deficient like boron.
Al(OC2H5)3
Al is Group III - electron deficient like boron.
This molecule is a Lewis acid.
Al(OC2H5)3
Al is Group III - electron deficient like boron.
This molecule is a Lewis acid.
O has lone pairs, it is a Lewis base
Al(OC2H5)3
Al is Group III - electron deficient like boron.
This molecule is a Lewis acid.
O has lone pairs, it is a Lewis base
The molecule is both a Lewis acid and base.
x3
Al ..
.
Al(OC2H5)3
Al(OC2H5)3
Covalent bonds
Al(OC2H5)3
Electron deficient
Al(OC2H5)3
Empirical formula
[Al(OC2H5)3]2
Al(OC2H5)3
Empirical formula
Molecular formula
[Al(OC2H5)3]2
dimer
[Al(OC2H5)3]2
dimer
Covalent bonds
[Al(OC2H5)3]2
dimer
Covalent bondsCoordinate covalent bonds
[Al(OC2H5)3]2
dimer
AlCl3
AlCl3
Empirical formula
AlCl3
Empirical formula
[AlCl3]2
Molecular formula
[AlCl3]2
s block
s blockp block
s blockp block
Main Group Elements
Oxides of s and p block elements
are acid and base anhydrides, with
definite trends in respect to the elements’
location in the periodic table.
Oxides of non-metals tend to be acid anhydridesOxides of metals tend to be base anhydrides
Structure and bonding in s and p block oxides
From: N. C. Norman Chapter 5
Norman: Chapter 6 should be read
for acid and base information.
Structure and bonding in s and p block oxides
From: N. C. Norman
Group numbers are changed in Norman.
Groups 1 - 18
3 4 5 6 7 8 9 10 11 12
13 14 15 16 17 18
Structure and bonding in s and p block oxides
Increasing electronegativity
Binary ionic compounds form
from elements having very
different electronegativities.
Binary ionic compounds form
from elements having very
different electronegativities.
Oxygen is high on the electronegativity scale, Rb and Ba have the lowest electronegativities of the metals on the Norman chart.
K2O : ionic material
K2O : ionic material
K2O(s) + H2O(l) 2 K+(aq) + O2-(aq)
K2O : ionic material
K2O(s) + H2O(l) 2 K+(aq) + O2-(aq)
O2-(aq) + H2O(l) 2 OH-(aq)
K2O : ionic material
K2O(s) + H2O(l) 2 K+(aq) + 2 OH-(aq)
Strong base
K2O : ionic material
K2O(s) + H2O(l) 2 K+(aq) + 2 OH-(aq)
Strong base
Base anhydride
Small differences in electronegativities
lead to covalent bonds.
Small differences in electronegativities
lead to covalent bonds.
SO3 : covalent molecule
SO3 : covalent molecule
SO3(g) + H2O(l) H2SO4(aq)
Strong acid
SO3 : covalent molecule
SO3(g) + H2O(l) H2SO4(aq)
Strong acid
Acid anhydride
Some of the polymeric oxides will
be amphoteric.
Some of the polymeric oxides will
be amphoteric.
They will act as acids or bases depending
on how acidic or basic the environment is.
Some of the polymeric oxides will
be amphoteric.
Al2O3(aq) + 6 H+(aq) 2 Al3+(aq) + 3 H2O(l)
Some of the polymeric oxides will
be amphoteric.
Al2O3(aq) + 6 H+(aq) 2 Al3+(aq) + 3 H2O(l)
Al2O3 reduces H+ = basic
Some of the polymeric oxides will
be amphoteric.
Al2O3(aq) + 6 H+(aq) 2 Al3+(aq) + 3 H2O(l)
Al2O3 reduces H+ = basic
Al2O3(aq) + 2 OH-(aq) + 3 H2O(l) 2 [Al(OH)4]-(aq)
Some of the polymeric oxides will
be amphoteric.
Al2O3(aq) + 2 OH-(aq) + 3 H2O(l) 2 [Al(OH)4]-(aq)
Al2O3 reduces OH- : acidic
Structures of polymeric oxides
quartz
SiO4
Empiricalformula
quartz
SiO4
Empiricalformula
quartz
SiO4
Empiricalformula
quartz
Tetrahedra share all cornersEach share = 1/2 O/Si
quartz
Tetrahedra share all cornersEach share = 1/2 O/Si
quartz
Tetrahedra share all cornersEach share = 1/2 O/Si
Binary compounds
with halogens
chlorides
chlorides
NaCl : ionic salt
chlorides
NaCl : ionic salt
CCl4 : dense liquid
chlorides
NaCl : ionic salt
CCl4 : dense liquid
BCl3 : gascovalent
chlorides
AlCl3 : dimer
chlorides
AlCl3 : dimer
GaCl3 : dimer
chlorides
AlCl3 : dimer
GaCl3 : dimer
chlorides
BeCl2 : infinite chain
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