Solution:
Species in which bond order is zero do not exist.
(1) \(\mathrm{O}_{2}=(K K)\left(\sigma 2 s^{2}\right)\left(\sigma^{*} 2 s^{2}\right)\left(\sigma 2 p_{z}^{2}\right)\)
\(\left(\pi 2 p_{x}^{2}=\pi 2 p_{y}^{2}\right)\left(\pi^{*} 2 p_{x}^{1}=\pi^{*} 2 p_{y}^{1}\right)\)
Bond Order \(=\frac{10-6}{2}=2\)
(2) \(H e_{2}=\left(\sigma 1 s^{2}\right)\left(\sigma^{*} 1 s^{2}\right)\)
Bond Order \(=0\)
(3) \(L i_{2}=\left(\sigma 1 s^{2}\right)\left(\sigma^{*} 1 s^{2}\right)\left(\sigma^{*} 2 s^{2}\right)\)
Bond Order \(=1\)
(4) \(C_{2}=\left(\sigma 1 s^{2}\right)\left(\sigma^{*} 1 s^{2}\right)\left(\sigma 2 s^{2}\right)\left(\sigma^{*} 2 s^{2}\right)\)
\(\left(\pi 2 p_{x}^{2}=\pi 2 p_{y}^{2}\right)\)
Bond Order \(=2\)
As, bond order of \(\mathrm{He}_{2}\) is zero it does not exist.
