Question

Which of the following options represents the correct bond order ?
A. `O_2^(-) gt O_2 gt O_2^+`
B. `O_2^(-) lt O_2 lt O_2^+`
C. `O_2^(-) gt O_2 gt O_2^+`
D. `O_2^(-) lt O_2 lt O_2^+`

Answer 1

Correct Answer - C
Bond order of `O_2^-`
`O_2^(-)=sigma1s^2,overset***sigma1s^2,sigma2s^2,overset***sigma2s^2, sigma2p_z^2(pi2p_x^2=pi2p_y^2)`
`(pi^***2p_x^1=pi^***2p_y^1)`
Bond order `="number of electrons in BMO - number of electrons ABMO"/2`
`=(10-7)/2=3/2=1.5`
`O_2^+=sigma1s^2,overset***sigma1s^2,sigma2s^2,overset***sigma2s^2 sigma2p_z^2(pi2p_x^2=pi2p_y^2)`
`(pi^***2p_x^1=pi^***2p_y^0)`
BO=`(10-5)/2=5/2=2.5`
`O_2^+=sigma1s^2,overset***sigma1s^2,sigma2s^2,overset***sigma2s^2 sigma2p_z^2(pi2p_x^2=pi2p_y^2)`
`(pi^***2p_x^1=pi^***2p_y^1)`
BO=`(10-6)/2=5/2=2.5`
So, the correct sequence is `O_2^(-) lt O_2 lt O_2^(+)`