POSTULATES Condition for bond formation Strength of the bond Energy of orbitals Spin of electrons Unstability

Binding Force Number of Covalent Bonds Geometry of Molecules Neutralisation of spins of electrons Stability of covalent bonds

INTERACTING FORCES e r e

OVERLAPPING OF ORBITALS s – s overlap Overlapping between two half filled s – orbitals of two different atoms containing unpaired electrons with opposite spins

s-s overlap

s – p overlap Overlap of one half filled ‘ s ‘ and one half filled ‘ p ‘ orbital of two different atoms containing unpaired electrons with opposite spins

s-p overlap

p – p overlap The overlap between half filled p orbital of one atom and half filled p orbital of another atom

p-p overlap

SIGMA BOND Bond formed by axial overlapping of atomic orbitals

Pi BOND Formed by sidewise overlapping of atomic orbitals

Comparison of Sigma & Pi bond Sigma bond Pi bond Formed by axial overlapping of atomic orbitals Formed by lateral overlapping of atomic orbitals Orbitals oriented along the internuclear axis Orbitals oriented perpendicular to the internuclear axis Extent of overlapping is more Extent of overlapping is less

only p orbitals are involved more energy is evolved less energy is evolved s and p orbitals are involved only p orbitals are involved Stronger than pi bond weaker than sigma bond Overlapping is symmetrical Overlapping is unsymmetrical