There are some species given below.
(i) ${\mathrm{O}}_2^{+}$

(ii) $\mathrm{CO}$ 

(iii) ${\mathrm{B}}_2$

(iv) ${\mathrm{O}}_2^{-}$

(v) ${\mathrm{NO}}^{+}$

(vi) ${\mathrm{He}}_2^{+}$

(vii) ${\mathrm{C}}_2^{2+}$

(viii) ${\mathrm{CN}}^{-}$

(ix) ${\mathrm{N}}_2^{-}$
The total number of species which have their fractional bond order is _____.