According
to Valance bond theory (VBT) by overlapping of atomic Orbitals three types of
covalent bond formation take place.
(1) Sigma Bond:
(2) Pi (π)-Bond:
(3) Delta Bond
Pi(π)
Bond:
(1) Pi (π) bond formed by
sideways/lateral overlapping of pure atomic orbitals except Benzene where
hybrid orbital formed π- bond.
(2) Lateral overlapping is only partial, so bonds formed are weaker and
hence more reactive than sigma bond (repulsion between nucleus is more as
orbitals have to come much close to each other for pi bond formation).
For
example-formation of oxygen molecule. Only Py and Pz of oxygen atom have
unpaired electron in each orbital for bonding.
Electronic
configuration of oxygen atom is 1s2,2s2,2Px2,Py1,Pz1
(3) Free rotation about a pi bond is not possible.
(4) pi bond is weaker than sigma bond .
(5) pi bond takes part in resonance.
(6) pi bond formed by pure or unhybrid orbitals.
Type
of π- bond:
(1)
Pπ-Pπ bond:
(2)
Pπ-dπ bond:
(3)
dπ-dπ bond:
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