Arrange the following species in order of increasing stability and give reasons: `Li_(2),Li_(2)^(+),Li_(2)^(-)`.

Explanation

Electronic configurations of `Li_(2),Li_(2)^(+) and Li_(2)^(-)` are as follows `[Li(Z=3)]`.
`Li_(2)-K K(sigma_(2s))^(2), thereforeB.O.=(2-0)/(2)=1`
`Li_(2)^(+)-K K(sigma_(2s))^(1), therefore B.O.=(1-0)/(2)=0.5`
`Li_(2)^(-)-K K(sigma_(2s))^(2)(sigma_(2s)^(**))^(1), therefore B.O.=(2-1)/(2)==0.5`
Greater the bond order, greater is the bond dissociation enthalpy and hence greater is the stability. again stability decreses when excess electrons are present in non-conjugate shell. thereofre the order of increasing stability of the given species are as follows:
`Li_(2)^(-) lt Li_(2)^(+) lt Li_(2)`.