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 resulting from atomic orbital overlap depends on orbital type, overlap extent, and energy compatibility. This explanation compares bond strengths of s-s, p-p, and s-p orbital overlaps.

1. Orbital Overlap Fundamentals:
   
   • s-Orbitals: Spherical, overlapping uniformly in all directions.
   • p-Orbitals: Directional lobes form end-to-end \( \sigma \)-bonds or side-by-side \( \pi \)-bonds.
   • s-p Overlap: Overlap between an s-orbital and a p-orbital.
2. Key Factors in Bond Strength:
   
   • Overlap Extent: Greater overlap yields stronger bonds due to increased electron density.
   • Energy Compatibility: Similar orbital energies lead to more effective overlap and stronger bonds.
   • Bond Type: \( \sigma \)-bonds (head-on) are typically stronger than \( \pi \)-bonds (side-by-side).
3. Overlap Type Analysis:
   
   • s-s Overlap:
     
     • Spherical orbitals provide maximum overlap.
     • Uniform overlap results in a strong \( \sigma \)-bond.
     • Example: H\(_2\) bond.
   • s-p Overlap:
     
     • Involves s and p orbitals.
     • Overlap is less extensive than s-s due to p-orbital directionality.
     • Forms a strong \( \sigma \)-bond due to effective head-on overlap.
     • Example: HCl bond.
   • p-p Overlap:
     
     • Involves two p-orbitals.
     • Forms \( \sigma \)-bonds (head-on) or \( \pi \)-bonds (side-by-side).
     • \( \pi \)-bonds are weaker than \( \sigma \)-bonds due to less effective overlap.
     • \( \sigma \)-overlap can be less extensive than s-s overlap.
     • Example: Cl\(_2\) bond.
4. Comparative Bond Strength:
   Bond Strength: \( \text{s-s} > \text{s-p} > \text{p-p} \)
   
   • s-s Overlap (A): Strongest due to maximal, uniform overlap.
   • s-p Overlap (C): Intermediate strength; effective but less extensive overlap.
   • p-p Overlap (B): Weakest; \( \pi \)-bonds are inherently weaker, and p-p \( \sigma \)-overlaps are typically weaker than s-s.
5. Conclusion:
   The decreasing order of bond strength based on orbital overlap is:
   \[ (A) \, \text{s-s} > (C) \, \text{s-p} > (B) \, \text{p-p} \] Therefore, option (4) (A), (C), (B) is correct.