Question

$N_2$ and $O_2$ are converted into monoanions, $N_2^{-}$ and $O_2^{-}$ respectively, which of the following statements is wrong?

• A. In $N_2^{-},N-N$ bond weakens
• B. In $O_2^{-},O-O$ bond ortder increases
• C. In $O_2^{-},O-O$ bond order decreases
• D. $N_2^{-}$ becomes paramagnetic

Answer 1

The correct option is B In $O_2^{-},O-O$ bond ortder increases

$O_2$ has two unpaired electrons in its ${\pi }^{\ast }$ orbitals, one electron goes to ${\pi }^{\ast }$ orbital to form $O_2{}^{-}$

Bond order in oxygen molecule ($O_2{}^{-}$)

$=0.5$ [(Number of bonding electrons) $–$ (number of anti-bonding electrons)]
$=0.5[10-7]$
$=1.5$

Therefore, bond order of $O_2{}^{-}$ decreases.

In the same way one electron goes to ${\pi }^{\ast }$ orbital to form $N_2{}^{-}$ and bond order decreases and it also become para magnetic.

Therefore, correct answer is $B$.