Old Material Revision
New Material
Chapter 8
one s orbital and one p orbital in the same shell combine forming two new orbitals named sp orbitals.
sp2 – hybridization
one s orbital and two p orbitals in the same shell combine forming three new orbitals named sp2 orbitals.
sp3– hybridization
one s orbital and three p orbitals in the same shell combine forming four new orbitals named sp 3 orbitals.
Summary of bonding orbitals, molecular shapes and bond angles
Trends of electronegativity
Polar molecules
Behaviour of Polar molecules in absence and presence of electric field
Strong dipoles
Weak dipoles
For a molecule to be polar
Molecules with polar bonds but no resultant dipole moment are non polar
Sigma bond
Pi bond
- When will a chemical bond form between two atoms :
- _Questions and Problems Chapter 5
- _Revision on Ionization Energy
- _Revision on Electron Dot Representation
New Material
Chapter 8
Hybridization :is the mixing of two or more atomic orbitals of similar energies in the same atom to produce new orbitals of equal energies.
Bond anglesp – hybridization
one s orbital and one p orbital in the same shell combine forming two new orbitals named sp orbitals.
The bond angle between the 2 sp orbitals is 180० to maximize the distance between the electrons
thus minimizing repulsions. This results in a linear geometry. Examples of molecules whose central
atoms exhibit sp hybridization include BeI₂, BeCl₂, BeF₂, BeBr2, BeH₂, CO₂
sp2 – hybridization
one s orbital and two p orbitals in the same shell combine forming three new orbitals named sp2 orbitals.
The bond angle between 2 sp2
orbitals is 120o to maximize the distance between the electrons
thus minimizing repulsions. This results in a triangular planar geometry. Examples of molecules
whose central atoms exhibit sp2
hybridization include halides of boron
sp3– hybridization
one s orbital and three p orbitals in the same shell combine forming four new orbitals named sp 3 orbitals.
The bond angle between 2 sp3
orbitals is 109.5o to maximize the distance between the electrons
thus minimizing repulsions. This results in a tetrahedral geometry. Examples of molecules whose central atoms exhibit sp3
hybridization include CI₄, CCl₄, CF₄, CBr₄, CH₄, SiI₄, SiCl₄, SiF₄, SiBr₄, SiH₄.
Beryllium and boron are said to be electron deficient in their compounds, they do not obey the octet rule.
Summary of bonding orbitals, molecular shapes and bond angles
In ammonia the central atom, N, exhibits sp3
hybridization: SQ9, 10
around the central atom (N) there are 3 bonds and 1 lone pair of electrons.
The lone pair of electrons affects the shape of nitrogen containing compounds.
The lone electrons are closer to the nitrogen atom than the electrons forming the covalent
bonds. This causes extra repulsion, forcing the three covalent bonds closer together. As a
result the ammonia molecule is pyramidal.
The H-N-H in ammonia is 107(rather than the expected 109.5for a tetrahedral structure).
In water the central atom, O, exhibits sp3
hybridization. SQ11, 12
Around the central atom (O) there are 2 bonds and 2 lone pairs of electrons.
The lone pair of electrons affects the shape of oxygen containing compounds.
The lone pair of electrons are closer to the oxygen atom than the electrons in the covalent
bonds. This causes extra repulsion, forcing the two covalent bonds closer together. As a result
the water molecule is V-shaped, or bent or angular.
The H-O-H in water is 104.5 (rather than the expected 109.5for a tetrahedral structure).
As number of lone pairs of electrons increases, the angle between bonding pairs decreases to reduce the repulsion between the electrons to the minimum.
Dative (coordinate) covalent bond
Electronegativity
Trends of electronegativity
Polar Covalent Bond
Dipoles
Polar molecules
Behaviour of Polar molecules in absence and presence of electric field
Strong dipoles
Weak dipoles
For a molecule to be polar
Molecules with polar bonds but no resultant dipole moment are non polar
Sigma bond
Pi bond
Isomers
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