Which of the following molecular species possess a fractional bond order (i.e., not a whole number)? — Chemical Bonding Chemistry Question

💡 Solution & Explanation

Fractional bond orders occur when an odd number of electrons occupy the molecular orbitals. $O_2^+$ has 15 $e^-$ (BO = 2.5). $O_2^-$ has 17 $e^-$ (BO = 1.5). $NO$ has 15 $e^-$ (BO = 2.5). $He_2^+$ has 3 $e^-$ (BO = 0.5). All of these species exhibit a fractional bond order.