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 :
$$B{e_2}$$
Solution :
$$B{e_2}:\left( {\sigma 1{s^2}} \right)\left( {{\sigma ^ * }1{s^2}} \right)\left( {\sigma 2{s^2}} \right)$$ $$\left( {{\sigma ^ * }2{s^2}} \right)$$
$$\eqalign{
& B.O. = \frac{1}{2}\left( {{N_b} - {N_a}} \right) \cr
& \,\,\,\,\,\,\,\,\,\,\,\,\, = \frac{1}{2} \times \left( {4 - 4} \right) \cr
& \,\,\,\,\,\,\,\,\,\,\,\,\, = 0 \cr} $$
Since $$B.O.$$ is zero, the molecule does not exist.