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AIIMS 201826 May
Exam
AIIMS
Year
2018
Date
26 May
Subject
Chemistry
Chapter
Chemical Bonding and Molecular Structure

AIIMS 2018 · 26 May · Chemistry · Chemical Bonding and Molecular Structure

Which of the following pairs does not have same bond order?

Which of the following pairs does not have same bond order?

Options

  1. AN2\mathrm{N}_2 and CN−\mathrm{CN}^{-}
  2. BO2+\mathrm{O}_2^{+}and NO\mathrm{NO}
  3. CF2−\mathrm{F}_2^{-}and O22−\mathrm{O}_2^{2-}
  4. DB22−\mathrm{B}_2^{2-} and CN+\mathrm{CN}^{+}

Correct answer

C. F2−\mathrm{F}_2^{-}and O22−\mathrm{O}_2^{2-}

Step-by-step solution

(a) N2(14):σ1s2σ∗1s2σ2s2σ⋆2s2π2px2=π2py2\mathrm{N}_2(14): \sigma 1 s^2 \sigma^* 1 s^2 \sigma 2 s^2 \sigma^{\star} 2 s^2 \pi 2 p_x^2=\pi 2 p_y{ }^2 σ2pz2\sigma 2 p_z^2 B.O. =12(Nb−Na)=12(10−4)=3.0=\frac{1}{2}\left(N_b-N_a\right)=\frac{1}{2}(10-4)=3.0 CN−(14):σ1s2σ∗1s2σ2s2σ∗2s2π2px2=π2py2\mathrm{CN}^{-}(14): \sigma 1 s^2 \sigma^* 1 s^2 \sigma 2 s^2 \sigma^* 2 s^2 \pi 2 p_x^2=\pi 2 p_y^2 σ2pz2\sigma 2 p_z^2 B.O. =12(10−4)=3.0=\frac{1}{2}(10-4)=3.0 (b) O2+(15):σ1s2σ∗1s2σ2s2σ∗2s2σ2pz2π2px2=\mathrm{O}_2^{+}(15): \sigma 1 s^2 \sigma^* 1 s^2 \sigma 2 s^2 \sigma^* 2 s^2 \sigma 2 p_z^2 \pi 2 p_x^2= π2py2π⋆2px1\pi 2 p_y^2 \pi^{\star} 2 p_x^1 B.O. =12(10−5)=2.5=\frac{1}{2}(10-5)=2.5 NO(15):σ1s2σ∗1s2σ2s2σ⋆2s2σ2pz2\mathrm{NO}(15): \sigma 1 s^2 \sigma^* 1 s^2 \sigma 2 s^2 \sigma^{\star} 2 s^2 \sigma 2 p_z^2 π2px2=π2py2π⋆2px1\pi 2 p_x^2=\pi 2 p_y^2 \pi^{\star} 2 p_x^1 B.O. =12(10−5)=2.5=\frac{1}{2}(10-5)=2.5 (c) F2−(19):σ1s2σ⋆1s2σ2s2σ⋆2s2σ2pz2π2px2=\mathrm{F}_2^{-}(19): \sigma 1 s^2 \sigma^{\star} 1 s^2 \sigma 2 s^2 \sigma^{\star} 2 s^2 \sigma 2 p_z^2 \pi 2 p_x^2= π2py2π⋆2px2=π∗2py2σ∗2pz1\pi 2 p_y^2 \pi^{\star} 2 p_x^2=\pi^* 2 p_y^2 \sigma^* 2 p_z^1 B.O. =12(10−9)=0.5=\frac{1}{2}(10-9)=0.5 O22−(18):σ1s2σ∗1s2σ2s2σ∗2s2σ2pz2π2px2=\mathrm{O}_2^{2-}(18): \sigma 1 s^2 \sigma^* 1 s^2 \sigma 2 s^2 \sigma^* 2 s^2 \sigma 2 p_z^2 \pi 2 p_x^2= π2py2π⋆2px2=π⋆2py2\pi 2 p_y^2 \pi^{\star} 2 p_x^2=\pi^{\star} 2 p_y^2 B.O. =12(10−8)=1.0=\frac{1}{2}(10-8)=1.0 (d) B22−(12):σ1s2σ⋆1s2σ2s2σ⋆2s2π2px2=π2py2\mathrm{B}_2^{2-}(12): \sigma 1 s^2 \sigma^{\star} 1 s^2 \sigma 2 s^2 \sigma^{\star} 2 s^2 \pi 2 p_x^2=\pi 2 p_y^2 B.O. =12(8−4)=2.0=\frac{1}{2}(8-4)=2.0 CN+(12):σ1s2σ∗1s2σ2s2σ∗2s2π2px2=π2py2\mathrm{CN}^{+}(12): \sigma 1 s^2 \sigma^* 1 s^2 \sigma 2 s^2 \sigma^* 2 s^2 \pi 2 p_x^2=\pi 2 p_y^2 B.O. =12(8−4)=2.0=\frac{1}{2}(8-4)=2.0
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