HYBRIDISATION

 

HYBRIDISATION

   ·      It is introduced by Pauling and Slater, to explain equivalent nature of covalent bonds in a molecule.

   ·      Mixing of different shape and approximate equal energy atomic orbitals, and redistribution of energy to form new orbitals, of same shape & same energy. These new orbitals are called hybrid orbitals and the phenomenon is called hybridization.

 Characteristic of Hybridization

(1) Hybridization is a mixing of orbitals and not electrons. Therefore, in hybridization full filled, half-filled and empty orbitals may take part.

(2) Number of the hybrid orbitals formed is always be equal  to number of atomic orbitals which  participates in the process of hybridization.

(3) The number of hybrid orbitals on central atom of a molecule or ion

 (4) One element can represent many hybridization state depending on experimental conditions for example, C showing sp, sp² and sp³ hybridization in its compounds.

(5) Hybrid orbitals are designated as sp, sp², sp³ etc.

 (6) The order of repulsion between lp – lp > lp – bp > bp – bp

(7) The directional properties in hybrid orbital is more than atomic orbitals. Therefore, hybrid orbitals form stronger sigma bond. The directional property of different hybrid orbitals will be in following order. sp < sp2 < sp3 < sp3d < sp3d 2 < sp3d3 since it depends upon the directional nature of orbitals.

Types of Hybridization

(A) sp hybridization

 (a) In this hybridization one s  & one p – orbital of an atom are mixed to give two new hybrid orbitals which are equivalent in shape & energy known as sp hybrid orbitals.

 (b) These two sp hybrid orbitals are arrange in straight line & at bond angle 180°.

(B) sp² Hybridization:

(a) In this hybridization one s & two p orbitals are mixed to give three new sp2 hybrid orbitals which are in same shape & equivalent energies.

 (b) These three sp2 hybrid orbitals are at angle of 120° & giving trigonal planar shape.

(C) sp³ Hybridization:

 (I) In this hybridization one  ‘ s’ orbital and three ‘p’ orbitals of an atom of a molecule or ion, are mixed to give four new hybrid orbitals called as sp3 hybrid orbitals.

 (II) The angle between hybrid orbitals will be 109° 28'

(D) sp³d Hybridization:

(I) In this hybridization one s orbital, three p orbitals and one d orbital are mixed to give five new hybrid orbitals which are equivalent in shape and energy called as sp3d hybrid orbitals.

(II) Out of these five hybrid orbitals, three hybrid orbitals are at 120° angle and two hybrid orbitals are perpendicular to the plane of three hybrid orbitals that is trigonal planar, the shape of molecule becomes trigonal bipyramidal. For example, PF5 showing sp3d hybridisation

(C) sp³d²Hybridisation:

 (I) In this hybridization, one s-orbital, three p-orbitals & two d-orbitals (dz2 , dx2–y2 ) are mixed to give six new hybrid orbitals known as sp3d 2 hybrid orbitals.

(II) The geometry of molecule obtained from above six hybrid orbitals will be symmetrical octahedral or square bipyramidal.

 (III) The angle between all hybrid orbitals will be 90°. Example: SF₆, AlF6 ^–3, PF₆ ^–, ICl5, XeF4, XeOF_4, ICl₄ ^–

(F) sp³d³ Hybridization:

(I) In this hybridization, one s-orbital, three p-orbitals & three d-orbitals are mixed to give seven new hybrid orbitals known as sp³d ³ hybrid orbitals.

(II) These seven sp³d ³ orbitals are configurated in pentagonal bipyramidal shape.

(III) Five bond angles are of 72° and 10 bond angles of 90°. (IV) The following examples showing sp3d 3 hybridization –IF₇ & XeF₆

_{explaination is coming soon}