According
to Valance bond theory (VBT) by overlapping of atomic Orbitals three types of
covalent bond formation take place.
(1) Sigma Bond:
(2) Pi Bond:
(3) Delta Bond:
Sigma
Bond:
(1)The sigma bond formed by nuclear/head on/axial overlapping /end
to end overlap of pure as well as hybrid atomic orbitals.
(2) Sigma bond do not involve in resonance.
(3) free rotation is possible about a single sigma bond.
(4) Maximum overlapping is possible between electron clouds and
hence it is strong bond.
(5) There can be only sigma bond between two atoms and sigma
bond are formed by three type of overlapping.
(A) S-S
overlapping: Two half filled s-orbitals
overlap along inter nuclear axis for example H2 molecule.
(B) s-p
overlapping : When half filled s-orbital
of one atom overlap with half with p-orbital of other atom for example HF
molecule.
(C) p-p
overlapping (Coaxial overlapping): it
involves the coaxial overlapping between half filled p-orbitals of two
different atoms for examples F2, Cl2, Br2 etc
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