Chemical Bonding and Molecular Structure - Result Question 93
####95. Which of the following pairs of species have the same bond order?
[2017]
(a) $O_2, NO^{+}$
(b) $CN^{-}, CO$
(c) $N_2, O_2^{-}$
(d) $CO, NO$
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Solution:
- (b) $CN^{-}$and $CO$ have same no. of electrons and have same bond order equal to 3 .
Short cut trick to calculate the bond order:
$N_2$ has 14 electrons and its bond order is 3 . We have to remember this concept that every electron added or subtracted to 14 , reduces the bond order by 0.5 . For example
$CN^{-} \Rightarrow$ no. of electrons $=6+7+1=14$
$\therefore$ bond order $=3$
$CO \Rightarrow$ no. of electrons $=6+8=14$
$\therefore$ bond order $=3$
NO $\Rightarrow$ no. of electrons $=7+8=15$
$\therefore$ bond order $=3-0.5=2.5$
$NO^{+} \Rightarrow$ no. of electrons $=7+8-1=14$
$\therefore$ bond order $=3$
$O_2{ }^{-} \Rightarrow$ no. of electrons $=8+8+1=17$
$\therefore$ bond order $=3-1.5$
Please note that this method will work for any species that have electrons between 10 and 18 .
