Question

Peroxide ion

• A. II and III
• B. I, II and IV
• C. I, III and IV
• D. I and IV

Answer 1

Answer: (A)

Peroxide ion is $O_2^{2-}.$ $O_2^{2-}(18)=\sigma 1s^2,\stackrel{\ast }{\sigma }1s^2,\sigma 2s^2,\stackrel{\ast }{\sigma }2s^2,\sigma 2p_z^2$ $\pi 2p_x^2\approx \pi 2p_y^2,\stackrel{\ast }{\pi }2p_x^2\approx \stackrel{\ast }{\pi }2p_y^2$ Bond order $=\frac{N_b-N_a}{2}$ $=\frac{10-8}{2}=1$ It contains four completely filled anti bonding molecular orbitals. Since, all the electrons are paired, $O_2^{2-}$ is diamagnetic. Peroxide ion is isoelectronic with argon, not with neon.