The pair of species with the same bond order is

The pair of species with the same bond order is
  1. $\mathrm{O}_2^{2-}, \mathrm{B}_2$
  2. $\mathrm{O}_2^{+}, \mathrm{NO}^{+}$
  3. $\mathrm{NO}, \mathrm{CO}$
  4. $\mathrm{N}_2, \mathrm{O}_2$

Solution

Bond order of \(\mathrm{O}_2{ }^{2-}\) :
Electronic : \(\sigma 1 \mathrm{~s}^2 \sigma^{\star}\left(\mathrm{s}^2 \sigma 2 \mathrm{~s}^2 \sigma^* 2 \mathrm{~s}^2 \sigma 2 \mathrm{P}_{\mathrm{z}}{ }^2\left(\pi 2 \mathrm{P}_{\mathrm{x}}{ }^2=\pi 2 \mathrm{P}_{\mathrm{y}}{ }^2\right)\right.\)
\(\left(\pi 2 \mathrm{P}_{\mathrm{x}}^2=\pi 2^{\star} \mathrm{P}_{\mathrm{y}}^2\right) \sigma^{\star} 2 \mathrm{pz}{ }^{\circ}\)
Bond order \(=\frac{\text { Bonding }- \text { Antibonding electrons }}{2}=\frac{10-8}{2}=1\)
Bond order of \(B_2\) :
\(\sigma 1 s^2 \sigma_{1 s}{ }^2 2 \sigma_{2 s} 2 \sigma^{\star} 2 s^2 \sigma 2 p_z^2\)
Bond order \(=\frac{6-4}{2}=1\)
\(\therefore \mathrm{O}_2{ }^{2-}\) and \(\mathrm{B}_2\) has same bond order 1.

Asked in: NEET 2012 (Screening)

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