Question

In which of the following molecules or ions, removal of one electron will increase the bond order and at the same time, make them diamagnetic from paramagnetic?

• A. $C{N}^{-}$
• B. $NO$
  
• C. $N_2$
  
• D. $O_2$
  

Answer 1

Answer: (B)

1. $C{N}^{-}$:

valence electrons=$4+5+1=10$

${\left(\sigma 2s\right)}^2{(\sigma \ast 2s)}^2{\left(\sigma 2p\right)}^2{\left(\pi 2p\right)}^4$

BO=$1/2\times (6-0)=3$;

2. $NO$:

valence electrons=$6+5=11$

${\left(\sigma 2s\right)}^2{(\sigma \ast 2s)}^2{\left(\sigma 2p\right)}^2{\left(\pi 2p\right)}^4{\left({\pi }^{\ast }2p\right)}^1$

BO=$1/2\times (6-1)=2.5$;

3.$O_2$:

valence electrons=$6+6=12$

${\left(\sigma 2s\right)}^2{(\sigma \ast 2s)}^2{\left(\sigma 2p\right)}^2{\left(\pi 2p\right)}^4{\left({\pi }^{\ast }2p\right)}^2$

BO=$1/2\times (6-2)=2$;

4. $N_2$:

valence electrons=$4+5+1=10$

${\left(\sigma 2s\right)}^2{(\sigma \ast 2s)}^2{\left(\sigma 2p\right)}^2{\left(\pi 2p\right)}^4$

BO=$1/2\times (6-0)=3$;

In case of $NO$, upon removal of one electron from anti-bonding orbital, the bond order increases from $2.5$ to $3$ and it becomes diamagnetic.