The bond order and magnetic property of acetylide ion (C22-) are same as that of

🧠 Find which species matches the bond order = 3 and diamagnetic character of the acetylide ion $\mathrm{C_2^{2-}}$ (14 electrons).

🗺️ MO analysis of $\mathrm{C_2^{2-}}$ (14 electrons):

\sigma_{1s}^2\sigma^*_{1s}^2\sigma_{2s}^2\sigma^*_{2s}^2\pi_{2p}^4\sigma_{2p}^2

BO = $(10-4)/2 = 3$; all electrons paired → diamagnetic

Check each option:

| Species | e⁻ | BO | Unpaired | Magnetic | |---------|----|----|---------|---------| | $\mathrm{O_2^+}$ | 15 | 2.5 | 1 | Paramagnetic | | $\mathrm{N_2^+}$ | 13 | 2.5 | 1 | Paramagnetic | | $\mathrm{NO^+}$ | 14 | 3 | 0 | Diamagnetic ✓ | | $\mathrm{O_2^-}$ | 17 | 1.5 | 1 | Paramagnetic |

⚡ $\mathrm{NO^+}$ is isoelectronic with $\mathrm{C_2^{2-}}$ (both 14e) → same MO filling → BO = 3, diamagnetic. Both are also isoelectronic with $\mathrm{N_2}$ and CO.

$\boxed{\text{Answer: } \mathrm{NO^+}}$