Question

The species having bond order different from that in CO is:

• A. NO^-
• B. NO⁺
• C. CN^-
• D. N₂

Answer 1

The correct option is A

NO^-

Whenever we want to determine the bond order, we draw the MO energy level diagrams and calculate the bond order.

So, let's have draw the MO energy level diagrams

Now, we can see that,

in $N{O}^{-}$ → we have to fill 1 more electron [Because '-' charge implies one more electron]

$N{O}^{+}$ → 1 less electron [Because + charge implies one less electron]

$C{N}^{-}$ → One more electron

Now, let's calculate bond order.

Bond order = 1/2 [Bonding electrons - Anti-Bonding electrons]

$CO$ ⇒ BO = $\frac{1}{2}\times [10-4]$ = 3

$N{O}^{-}$ ⇒ BO = $\frac{1}{2}\times [10-6]$ = 2 [Different]

$N{O}^{+}$ ⇒ BO = $\frac{1}{2}\times [10-4]$ = 3 [Same]

$C{N}^{-}$ ⇒ BO = $\frac{1}{2}\times [10-4]$ = 3 [Same]

$N_2$ ⇒ BO = $\frac{1}{2}\times [10-4]$ = 3 [Same]

Therefore, $N{O}^{-}$ has a different bond order from that of $CO$.