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NEET CHEMISTRYOrganic Chemistry – Some Basic Principles and Techniques Medium

Question

The correct order of increasing bond order among the given is:

A

O₂⁻ < NO < C₂²⁻ < He₂⁺

B

NO < C₂²⁻ < O₂⁻ < He₂⁺

C

C₂²⁻ < He₂⁺ < NO < O₂⁻

D

He₂⁺ < O₂⁻ < NO < C₂²⁻

Step-by-Step Solution

  1. Formula: Bond Order (B.O.) = 12(Nb−Na)\frac{1}{2} (N_b - N_a).

  2. Analyze He₂⁺:

  • Total electrons: 2+2−1=32 + 2 - 1 = 3.
  • Configuration: σ1s2σ1s∗1\sigma_{1s}^2 \sigma_{1s}^{*1}.
  • B.O. = 12(2−1)=0.5\frac{1}{2} (2 - 1) = 0.5.
  1. Analyze O₂⁻ (Superoxide ion):
  • Total electrons: 8+8+1=178 + 8 + 1 = 17.
  • Configuration: σ1s2σ1s∗2σ2s2σ2s∗2σ2pz2(π2px2=π2py2)(π2px∗2=π2py∗1)\sigma_{1s}^2 \sigma_{1s}^{*2} \sigma_{2s}^2 \sigma_{2s}^{*2} \sigma_{2p_z}^2 (\pi_{2p_x}^2 = \pi_{2p_y}^2) (\pi_{2p_x}^{*2} = \pi_{2p_y}^{*1}).
  • Nb=10,Na=7N_b = 10, N_a = 7.
  • B.O. = 12(10−7)=1.5\frac{1}{2} (10 - 7) = 1.5.
  1. Analyze NO:
  • Total electrons: 7+8=157 + 8 = 15.
  • Similar to O2+O_2^+. Configuration ends in π∗\pi^* having 1 electron.
  • Nb=10,Na=5N_b = 10, N_a = 5.
  • B.O. = 12(10−5)=2.5\frac{1}{2} (10 - 5) = 2.5.
  1. Analyze C₂²⁻ (Acetylide ion):
  • Total electrons: 6+6+2=146 + 6 + 2 = 14. Isoelectronic with N2N_2.
  • Configuration: σ1s2σ1s∗2σ2s2σ2s∗2(π2px2=π2py2)σ2pz2\sigma_{1s}^2 \sigma_{1s}^{*2} \sigma_{2s}^2 \sigma_{2s}^{*2} (\pi_{2p_x}^2 = \pi_{2p_y}^2) \sigma_{2p_z}^2.
  • Nb=10,Na=4N_b = 10, N_a = 4.
  • B.O. = 12(10−4)=3.0\frac{1}{2} (10 - 4) = 3.0.
  1. Conclusion: Increasing order is 0.5<1.5<2.5<3.00.5 < 1.5 < 2.5 < 3.0, which corresponds to He2+<O2−<NO<C22−He_2^+ < O_2^- < NO < C_2^{2-}.

Exam Context & Concepts Covered

This question aligns with the NEET CHEMISTRY syllabus, specifically targeting concepts from Organic Chemistry – Some Basic Principles and Techniques . 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.

CHEMISTRYOrganic Chemistry – Some Basic Principles and Techniques correctincreasing

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