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

$\sigma 1 s ^{2}, \sigma^{*} 1 s^{2}, \sigma 2 s^{2}, \sigma^{*} 2 s^{2}, \sigma 2 p_{z}^{2},\left[\pi 2 p_{x}^{2}=\pi 2 p_{y}^{2}\right\}$

$\left[\pi^{*} 2 p_{x}^{2}=\pi^{*} 2 p_{y}^{2}\right], \sigma^{*} 2 p_{z}^{0}$

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

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

Number of unpaired electrons $=0$

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