Question

Give reasons for :
(a) Sigma (6) bond is stronger than pi (7) bond.
(b) HF is a polar molecule.​

Answer 1

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(a) (i) Sigma (6) bond is formed by coaxial overlapping while pi (π) bond is formed by sidewise or colateral overlapping of atomic orbitals of bonding atoms.

(ii) Hence the extent of overlapping in a sigma (Φ) bond is greater than in pi (π) bond.

(iii) The bond enthalpy of a sigma bond is higher than pi bond. Therefore sigma bond is stronger than pi bond.

(b) In HF molecule, fluorine being highly electronegative, there is a partial shift of electron bond pair towards F atom, making it partially negative and H atom partially positive. Hence HF is a polar molecule