Question

The decreasing strength of bond formed by overlap of
(A). s-s
(B). p-p
(C). s-p
follows the order
Choose the correct answer from the options given below:

• A. (C), (A), (B).
• B. (B), (A), (C)
• C. (A), (B), (C)
• D. (A), (C), (B)

Hint:

The strength of a chemical bond is influenced by the type of atomic orbitals involved and the nature of their overlap. Generally, s-s overlaps form the strongest bonds due to maximum overlap, followed by s-p overlaps, and then p-p overlaps which can form weaker bonds.

Answer 1

The Correct Option is D

The strength of a chemical bond formed by the overlap of atomic orbitals depends on several factors, including the type of orbitals involved, the extent of their overlap, and the energy compatibility between them. Here, we are comparing the bond strengths formed by different types of orbital overlaps: s-s, p-p, and s-p.

1. Understanding Orbital Overlap:
   
   • s-Orbitals: Spherically symmetrical and can overlap uniformly in all directions.
   • p-Orbitals: Have directional lobes and can overlap end-to-end (\( \sigma \)-bonds) or side-by-side (\( \pi \)-bonds).
   • s-p Overlap: Involves the overlap between an s-orbital and a p-orbital.
2. Factors Affecting Bond Strength:
   
   • Extent of Overlap: Greater overlap between orbitals leads to stronger bonds due to increased electron density between nuclei.
   • Energy Compatibility: Orbitals with similar energies overlap more effectively, resulting in stronger bonds.
   • Bond Type: \( \sigma \)-bonds (head-on overlap) are generally stronger than \( \pi \)-bonds (side-by-side overlap).
3. Analyzing Each Overlap Type:
   
   • s-s Overlap:
     
     • Both orbitals are spherically symmetrical and have maximum overlap.
     • The uniform overlap leads to a strong \( \sigma \)-bond.
     • Example: The bond in H\(_2\) molecule.
   • s-p Overlap:
     
     • Involves one s-orbital and one p-orbital.
     • The overlap is not as extensive as s-s because p-orbitals have directional lobes.
     • However, the bond is still strong due to effective head-on overlap forming a \( \sigma \)-bond.
     • Example: The bond in HCl molecule.
   • p-p Overlap:
     
     • Involves two p-orbitals.
     • Can form \( \sigma \)-bonds (head-on) or \( \pi \)-bonds (side-by-side).
     • \( \pi \)-bonds are generally weaker than \( \sigma \)-bonds due to less effective overlap.
     • Even when forming \( \sigma \)-bonds, the overlap may be less extensive compared to s-s overlap.
     • Example: The bond in Cl\(_2\) molecule.
4. Comparative Analysis:
   Bond Strength: \( \text{s-s} > \text{s-p} > \text{p-p} \)
   
   • s-s Overlap (A): Strongest due to maximum and uniform overlap.
   • s-p Overlap (C): Intermediate strength due to effective but less extensive overlap.
   • p-p Overlap (B): Weakest as \( \pi \)-bonds are less strong, and even p-p \( \sigma \)-overlaps are generally weaker than s-s.
5. Conclusion:
   Based on the above analysis, the decreasing order of bond strength formed by the overlap of the given orbitals is:
   \[ (A) \, \text{s-s} > (C) \, \text{s-p} > (B) \, \text{p-p} \] Therefore, the correct option is (4) (A), (C), (B).