There are some species given below :-
`{:((a)O_(2)^(+),,,,(b)CO),((c)B_(2),,,,(d)O_(2)^(+)),((e)NO^(+),,,,(f)He_(2)^(+)),((g)C_(2)^(+2),,,,(h)CN^(-)),((i)N_(2)^(-),,,,):}`
Total no. of species which have their fractional bond order.

Answer

`4`

Explanation

`to` molecular orbital configuration for upto 14 electrons
`sigma_(1s)ltoverset("*")(sigma_(1s))ltsigma_(2s)ltoverset("*")(sigma_(2s))ltpi_(2px)pi_(2py)ltsigma_(2px)ltoverset("*")(pi_(2px))=overset("*")(pi_(2py))ltoverset("*")(simga_(2px))`
For more than 14 electrons `sigma_(1s)ltoverset("*")(sigma_(1s))ltsigma_(2s)ltoverset("*")(sigma_(2s))ltpi_(2px)=pi_(2py))ltoverset("*")(pi_(2px))=overset("*")(pi_(2py))ltoverset("*")(pi_(2px))`
Bond order `=(1)/(2)` number of electron in [Bonding M.O.-Antibonding M.O.]