Hybridization

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 angle

sp – 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 109.5for 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 109.5for 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.