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NEET CHEMISTRYChemical Bonding and Molecular StructureEasy

Question

An electron-deficient compound among the following is:

A

(SiH₃)₂

B

(BH₃)₂

C

PH₃

D

(CH₃)₂

Step-by-Step Solution

  1. Analyze Octet Fulfillment:
  • (CH₃)₂ (Ethane): Carbon (Group 14) has 4 valence electrons. It forms 4 sigma bonds (3 with H, 1 with C), resulting in a complete octet (8 electrons).
  • (SiH₃)₂ (Disilane): Silicon (Group 14) acts similarly to Carbon, forming 4 bonds and completing its octet.
  • PH₃ (Phosphine): Phosphorus (Group 15) has 5 valence electrons. It forms 3 bonds with H and possesses 1 lone pair. Total valence electrons = 2(lonepair)+6(bonding)=82(lone pair) + 6(bonding) = 8. Octet is complete.
  • (BH₃)₂ (Diborane): Boron (Group 13) has 3 valence electrons. In the monomer BH3BH_3, Boron forms 3 bonds, sharing 6 electrons. This is an incomplete octet (6 < 8), making it electron-deficient. It behaves as a Lewis acid (electron acceptor) [Concept of Lewis acids defined in Class 12 Chemistry, Unit 5, Sec 5.2]. To stabilize, it dimerizes to (BH3)2(BH_3)_2 using 3-center-2-electron bonds.

(Note: Specific details of diborane structure are from standard chemistry curriculum outside the provided text fragments.)

Exam Context & Concepts Covered

This question aligns with the NEET CHEMISTRY syllabus, specifically targeting concepts from Chemical Bonding and Molecular Structure. Mastering this topic is crucial for scoring well in the upcoming medical entrance examinations. Solving conceptually related problems will help you understand the nuances of these concepts and improve your problem-solving speed.

CHEMISTRYChemical Bonding and Molecular Structureelectrondeficientcompoundfollowing

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