Q38 / 155 · WBJEE 2018 · Chemistry

Which statements are correct for the peroxide ion?

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

Solution

The correct statements for peroxide ion $\left(\mathrm{O}_{2}^{2-}\right)$ are that it is diamagnetic and it has bond order one. Electronic configuration of $\mathrm{O}_{2}^{2-}$ (peroxide ion) is $\sigma \mathrm{l} s^{2}, \sigma^{*} 1 s^{2}, \sigma 2 s^{2}, \sigma^{*} 2 s^{2}, \sigma 2 p_{z}^{2},\left[\pi 2 p_{x}^{2}=\pi 2 p_{y}^{2}\right\}$ $$ \left[\pi^{\prime} 2 p_{x}^{2}=\pi^{*} 2 p_{y}^{2}\right], \sigma^{*} 2 p_{t}^{0} $$ $\because$ Bond order $=$ No. of electrons present in bonding No. of electrons present in non - bonding $\therefore \quad B O=\frac{10-8}{2}=\frac{2}{2}=1$ Number of unpaired electrons $=0$ $\mathrm{So}, \mathrm{O}_{2}^{2-}$ is diamagnetic in nature.

Hence, the correct answer is options: 'B', 'C'.

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