Question

Give any three main postulates of valence bond theory (VBT).

Answer 1

Postulates of valance bond theory-

• The overlapping of two half-filled valence orbitals of two different atoms results in the formation of the covalent bond. Due to overlapping, the electron density between two bonded atoms increases and this gives stability to the molecule.
  
• In case the atomic orbitals possess more than one unpaired electron, more than one bond can be formed and electrons paired in the valence shell cannot take part in such a bond formation.
  
• A covalent bond is directional and it is parallel to the region of overlapping atomic orbitals.
  
• Based on the pattern of overlapping, there are two types of covalent bonds: sigma bond and a pi bond. The covalent bond formed by sideways overlapping of atomic orbitals is known as pi bond whereas the bond formed by overlapping of atomic orbital along the inter nucleus axis is known as a sigma bond.