Question

Which statements are correct for the peroxide ion?

• A. It has five completely filled anti-bonding molecular orbitals.
• B. It is diamagnetic
• C. It has bond order one
• D. It is isoelectronic with neon

Answer 1

Answer: (B), (C)

The correct statements for peroxide ion $\left(O_2^{2-}\right)$ are that it is diamagnetic and it has bond order one.

Electronic configuration of $O_2^{2-}$ (peroxide ion) is

$\sigma 1s^2,{\sigma }^{\ast }1s^2,\sigma 2s^2,{\sigma }^{\ast }2s^2,\sigma 2p_z^2,\left[\pi 2p_x^2=\pi 2p_y^2\right\}$

$\left[{\pi }^{\ast }2p_x^2={\pi }^{\ast }2p_y^2\right],{\sigma }^{\ast }2p_z^0$

$\because$ Bond order
$=\frac{\text{ No. of electrons present in bonding - No. of electrons present in non - bonding }}{2}$

$\therefore BO=\frac{10-8}{2}=\frac{2}{2}=1$

Number of unpaired electrons $=0$

So, $O_2^{2-}$ is diamagnetic in nature.