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

Options

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

Answer

D

Explanation

The molecular orbital configuration of
`O_(2)^(-) ( 8 + 8 + 1 = 17) = sigma1s^(2),sigma **1s^(2),sigma 1s^(2),sigma2s^(2)`
`sigma2s^(2) sigma 2p_(x)^(2) pi 2p_(y)^(2) =~ pi** 2p_(y)^(2) =~ pi** 2p_(x)^(2)`
B.O. `= (N_(0) - N_(0))/(2) = (10 = 7)/(2) = 1.5`
No `(7 + 8 = 15) = sigma 1s^(2),sigma**1s^(2),sigma2s^(2)`
`sigma**2s^(2)sigma 2p_(x)^(2)pi 2p_(y)^(2) = pi 2p_(y)^(1) = pi**2p_(z)^(0)`
`B O = (N_(0) - N_(0))/(2) = (10 - 5)/(2) = 2.5`
For `C_(2)^(2-) = (10 - 4)/(2) = 3 `and `He_(2)^(+) = (2 - 1)/(2) = (1)/(5) = 0.5`
Hence the order is `He_(2)^(+) lt O_(2)^(-) lt NO lt C_(2)^(2-)`