Question

Which of the following has the shortest bond length?

• A. $O_2$
• B. $O_2^{-}$
• C. $O_2^{+}$
• D. $O_2^{2-}$

Answer 1

Answer: (C)

$O_2^{+}$

Answer $O_2^{+}$

Electronic configuration of $O_2$

$\sigma 1s^2{\sigma }^{\ast }1s^2\sigma 2s^2{\sigma }^{\ast }2s^2\sigma 2p_z^2,\pi 2p_x^2=\pi 2p_7^2,{\pi }^{\ast }2p_x^1={\pi }^{\ast }2p_7^1$

Bond order $=\frac{1}{2}$ (No. of bonding electrons-$-$ no. of antibonding electrons)$=\frac{1}{2}[10-6]=2$

Similarly for $O_2^{-}$

Bond order$=\frac{1}{2}[10-7]=1.5$

for $O_2^{2-}$

Bond order$=\frac{1}{2}[10-8]=1$

for $O_2^{+}$

Bond order$=\frac{1}{2}[10-5]=2.5$

Bond order is inversely proportional to bond length, $O_2^{+}$ has the shortest bond length.