According to molecular orbital theory, which of the following diatomic molecules does not exist?

Step-by-step solution

Total number of electrons in Be ₂ is 8. Its molecular orbital electronic configuration is 1s^2 ^ * 1s^2 2s^2 ^ * 2s^2 . Here, the number of bonding electrons ( N_b ) = 4 and the number of antibonding electrons ( N_a ) = 4. Bond order = 1 2 [N_b - N_a] = 1 2 [4 - 4] = 0 . Since the bond order is zero, the Be ₂ molecule does not exist. Li ₂ (6 electrons), B ₂ (10 electrons), and C ₂ (12 electrons) have bond orders of 1, 1, and 2 respectively, so they are stable and exist. Answer: Be ₂