Question

According to molecular orbital theory, which of the following will not exist?

• A. $H_2^{+}$
• B. $B{e}_2$
• C. $B_2$
• D. $C_2$

Answer 1

Answer: (B)

$B{e}_2:\left(\sigma 1s^2\right)\left({\sigma }^{\ast }1s^2\right)\left(\sigma 2s^2\right)\left({\sigma }^{\ast }2s^2\right)$
$B.O.=\frac{1}{2}(N_b-N_a)$
$=\frac{1}{2}\times (4-4)=0$
Since $B.O$. is zero, the molecule does not exist.