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4.Chemical Bonding and Molecular Structure
medium
Four diatomic species are listed below. Identify the correct order in which the bond order is increasing in them
A
$NO < O_{2}^- < C_2^{2-} < He_2^+$
B
$O_2^- < NO < C_2^{2-} < He_2^+$
C
$C_2^{2-} < He_2^+ < O_2^- < NO$
D
$He_2^+ < O_2^- < NO < C_2^{2-}$
(AIPMT-2008) (AIPMT-2012)
Solution
Bond order $=\frac{N_{b}-N_{2}}{2}$
(where $\mathrm{N}_{\mathrm{b}}=$ number of electrons in bonding molecular orbital $\mathrm{N}_{\mathrm{a}}=$ number of electrons in anti – bonding molecular orbital)
$\begin{array}{|c|c|}\hline \text { Diatomic species } & {\text { Bond order }} \\ \hline N 0 & {2.5} \\ {O_{2}^{-}} & {1.5} \\ {C_{2}^{2-}} & {3.0} \\ {H e_{2}^{+}} & {0.5} \\ \hline\end{array}$
Thus, increasing order: $\mathrm{He}_{2}^{+}<\mathrm{O}_{2}^{-}<\mathrm{NO}<\mathrm{C}^{2-}$
Std 11
Chemistry
