Stability of the species `Li_(2), Li_(2)^(-) and Li_(2)^(+)` increases in the order of:

Options

A. `Li_(2) lt Li_(2)^(+) lt Li_(2)^(-)`
B. `Li_(2)^(-) lt Li_(2)^(+) lt Li_(2)`
C. `Li_(2) lt Li_(2)^(-) lt Li_(2)^(+)`
D. `Li_(2)^(-) lt Li_(2) lt Li_(2)^(+)`

Answer

B

Explanation

`Li_(2)(3+3=6)=sigma1s^(2), overset(***)sigma1s^(2), sigma 2s^(2) " " ` Bond order `=(N_(b)-N_(a))/(2)=(4-2)/(2)=1`
`Li_(2)^(+) (3+3-1=5)=sigma1s^(2), overset(***)sigma1s^(2), sigma 2s^(1) " "` Bond order `=(3-2)/(2)=(1)/(2)=0.5`
`Li_(2)^(-) (3+3+1=7)=sigma1s^(2), overset(***)sigma2s^(2), sigma2s^(2), overset(***)sigma2s^(1)" "` Bond order `=(4-3)/(2)=(1)/(2)=0.5`
Stability order is `Li_(2)^(-) lt Li_(2)^(+) lt Li_(2)` (because `Li_(2)^(-)` has more number of electrons in antibonding orbitals which destabilises the species).