Question

Which of the following molecules exist?

• A. $H{e}_2$
• B. $B{e}_2$
• C. $N{e}_2$
• D. $C_2$

Answer 1

Answer: (D)

$H{e}_2:\sigma 1s^2,{\sigma }^{\ast }1s^2$
B.O. = $\frac{1}{2}(2-2)=0,H{e}_2$ does not exist.
$B{e}_2:\sigma 1s^2,{\sigma }^{\ast }1s^2,{\sigma }^{\ast }2s^2$
B.O. $=\frac{1}{2}(4-4)=0,B{e}_2$ does not exist.
$N{e}_2=\sigma 1s^2,{\sigma }^{\ast }1s^2,\sigma 2s^2,{\sigma }^{\ast }2s^2,\sigma 2p_z^2,\left(\pi 2p_x^2=\pi 2p_y^2\right)\left({\pi }^{\ast }2p_x^2={\pi }^{\ast }2p_y^2\right),{\sigma }^{\ast }2p_z^2$
B.O. $=\frac{1}{2}\left(10-10\right)=0,N{e}_2$does not exist.
$C_2:\sigma 1s^2,{\sigma }^{\ast }1s^2,\sigma 2s^2,{\sigma }^{\ast }2s^2,(\pi 2p_x^2=\pi 2p_y^2)$
B.O $=\frac{1}{2}\left(8-4\right)=2,C_2$ exists.