1. Tardigrade
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  4. Bond order normally gives idea of stability of a molecular species. All the molecules viz. H2, Li2 and B2 have the same bond order yet they are not equally stable. Their stability order is

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Q. Bond order normally gives idea of stability of a molecular species. All the molecules viz.$ H_2, Li_2$ and $B_2$ have the same bond order yet they are not equally stable. Their stability order is

Chemical Bonding and Molecular Structure

Solution:

The molecular orbital configuration of the given molecules is
$H _2=\sigma 1 s^2$ (no anti-bonding electron)
$Li _2=\sigma 1 s^2 \sigma^* 1 s^2 \sigma 2 s^2$ (two anti-bonding electrons)
$B _2=\sigma 1 s^2 \sigma^* 1 s^2 \sigma 2 s^2 \sigma^* 2 s^2\left\{\pi 2 p_y^1=\pi 2 p_z^1\right\}$
(4 anti-bonding electrons)
Though the bond order of all the species are same $(B . O=1)$ but stability is different. This is due to difference in the presence of no. of anti-bonding electrons.
Higher the no. of anti-bonding electron, lower is the stability, hence the correct order is $H _2> Li _2> B _2$