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NEET 2018
Exam
NEET
Year
2018
Subject
Chemistry
Chapter
Chemical Bonding and Molecular Structure

NEET 2018 · Chemistry · Chemical Bonding and Molecular Structure

Consider the following species, CN ^ + , CN ^ - 1 , NOandCN Which...

Consider the following species,

CN+,CN−1,NOandCN{CN}^{+}, {CN}^{- 1}, NOandCN

Which one of these will have the highest bond order?

Options

  1. ACN+{CN}^{+}
  2. BCN−{CN}^{-}
  3. CNONO
  4. DCNCN

Correct answer

B. CN−{CN}^{-}

Step-by-step solution

Ion/Species Total electron Bond order
NONO 1515 2.52 . 5
CN−{CN}^{-} 1414 33
CN+{CN}^{+} 1212 22
CNCN 1313 2.52 . 5


Number of e−{e}^{-} in NO=7+8=15NO = 7 + 8 = 15

NO=σ1s2<σ∗1s2<σ2s2<σ∗2s2<σ2Pz2<π2Py2=π2Px2<π∗2Py1=π∗2Px0NO = \sigma1{s}^{2} < \overset{*}{\sigma}1{s}^{2} < \sigma2{s}^{2} < \overset{*}{\sigma}2{s}^{2} < \sigma2{P}_{z}^{2} < \pi2{P}_{y}^{2} = \pi2{Px}^{2} < \overset{*}{\pi}2{P}_{y}^{1} = \overset{*}{\pi}2{P}_{x}^{0}

Bond order =(number of electron in bonding molecular orbital - number of electroninantibondingmolecularorbital)2= \dfrac{\text{(number of electron in bonding molecular orbital - number of electron}inantibondingmolecularorbital )}{2}

BO=6−12=2.5BO = \dfrac{6 - 1}{2} = 2 .5 .

Number of e−{e}^{-} in CN=6+7=13CN = 6 + 7 = 13

NO=σ1s2<σ∗1s2<σ2s2<σ∗2s2<σ2Pz2<π2Py2=π2Px2<π∗2Py1=π∗2Px0NO = \sigma1{s}^{2} < \overset{*}{\sigma}1{s}^{2} < \sigma2{s}^{2} < \overset{*}{\sigma}2{s}^{2} < \sigma2{P}_{z}^{2} < \pi2{P}_{y}^{2} = \pi2{Px}^{2} < \overset{*}{\pi}2{P}_{y}^{1} = \overset{*}{\pi}2{P}_{x}^{0}.

Bond order =52=2.5= \dfrac{5}{2} = 2.5

Number of e−{e}^{-} in CN+=6+7−1=12{CN}^{+} = 6 + 7 - 1 = 12

NO=σ1s2<σ∗1s2<σ2s2<σ∗2s2<σ2Pz2<π2Py2=π2Px2<π∗2Py1=π∗2Px0NO = \sigma1{s}^{2} < \overset{*}{\sigma}1{s}^{2} < \sigma2{s}^{2} < \overset{*}{\sigma}2{s}^{2} < \sigma2{P}_{z}^{2} < \pi2{P}_{y}^{2} = \pi2{Px}^{2} < \overset{*}{\pi}2{P}_{y}^{1} = \overset{*}{\pi}2{P}_{x}^{0}

Bond order =4−02=2= \dfrac{4 - 0}{2} = 2

CN−={CN}^{-} = number of e−{e}^{-} in CN−=6+7+1=14{CN}^{-} = 6 + 7 + 1 = 14

CN−=σ1s2<σ∗1s2<σ2s2<σ∗2s2<σ2Pz2<π2Py2=π2Px2<π∗2Py1=π∗2Px0{CN}^{-} = \sigma1{s}^{2} < \overset{*}{\sigma}1{s}^{2} < \sigma2{s}^{2} < \overset{*}{\sigma}2{s}^{2} < \sigma2{P}_{z}^{2} < \pi2{P}_{y}^{2} = \pi2{Px}^{2} < \overset{*}{\pi}2{P}_{y}^{1} = \overset{*}{\pi}2{P}_{x}^{0}

Bondorder = \dfrac{6 - 0}{2} = 3.<br/><br/>.<br /><br />{CN}^{-} as highest bond order.
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