Four diatomic species are listed in different sequence .Which of these represent the correct order of their increasing bond order?

Options

A. `C_(2)^(2-) lt He_(2)^(+) lt NO lt O_(2)^(-)`
B. `He_(2)^(+) lt O_(2)^(-) lt NO ltC_(2)^(2-)`
C. `O_(2)^(-) lt NO lt C_(2)^(2-)ltHe_(2)^(+)`
D. `NOltC_(2)^(2-)ltO_(2)^(-)ltHe_(2)^(+)`

Answer

B

Explanation

`C_(2)^(2-)[sigma_(1s)]^(2)[sigma_(1s)^(**)]^(2)[sigma_(2s)]^(2)[sigma_(2s)^(**)]^(2)[pi_(2px)]^(2)=[pi_(2py)]^(2)[sigma_(2py)]^(2)`
`B.O.=1//2[10-4]=3`
`He_(2)^(+):[sigma_(1s)]^(2)[sigma_(1s)^(**)]^(1)`
`B.O.1//2[2-1]=1//2=0.5`
`NO: [sigma_(1s)]^(2)[sigma_(1s)^(**)]^(2)[sigma_(2s)]^(2)[sigma_(2s)^(**)][pi_(2px)]^(2)`
`=[pi_(2py)]^(2)[sigma_(2pz)]^(2)[pi_(2px)^(**)]^(1)`
`B.O.=1//2[10-5]=2.5`
`O_(2)^(-):[sigma_(1s)]^(2)[sigma_(1s)^(**)]^(2)[sigma_(2s)]^(2)[sigma_(2s)^(**)]^(2)[pi_(2px)]^(2)=[pi_(2py)]^(2)`
`[pi_(2px)^(**)]^(2)[pi_(2py)^(**)]^(1)`
`B.O.=1//2[10-7]=1.5`
Correct order : `He^(2+)ltO_(2)^(-)ltNO ltC_(2)^(2-)`