Question

Which of the following facts regarding change in bond length is correct?

• A. Increases in going from $N_2$ to $N_2^{+}$, decreases in going from $O_2$ to $O_2^{+}$
• B. Decreases in going from $N_2$ to $N_2^{+}$, decreases in going from $O_2$ to $O_2^{+}$
• C. Increases in going from $N_2$ to $N_2^{+}$ and $O_2$ to $O_2^{+}$
• D. Decreases in going from $N_2$ to $N_2^{+}$ and $O_2$ to $O_2^{+}$

Answer 1

The correct option is A Increases in going from $N_2$ to $N_2^{+}$, decreases in going from $O_2$ to $O_2^{+}$

The electronic configuration of $N_2$ and $O_2$ are as follows:
$N_2:\sigma \left(1s{)}^2{\sigma }^{\ast }\right(1s^2\left)\sigma \right(2s{)}^2{\sigma }^{\ast }\left(2s{)}^2\pi \right(2p_x{)}^2\pi \left(2p_y{)}^2\sigma \right(2p_z{)}^2$
$O_2:\sigma \left(1s{)}^2{\sigma }^{\ast }\right(1s^2\left)\sigma \right(2s{)}^2{\sigma }^{\ast }\left(2s{)}^2\sigma \right(2p_z{)}^2\pi \left(2p_x{)}^2\pi \right(2p_y{)}^2{\pi }^{\ast }\left(2p_x{)}^1{\pi }^{\ast }\right(2p_y{)}^1$
Going from $N_2$ to $N_2^{+}$, one bonding electron is removed. This decreases the bond order and hence increases the bond length. Going from $O_2$ to $O_2^{+}$, one antibonding electron is removed. This increases the bond order and hence decreases the bond length.