Stability of the species Li2,Li2-and Li2+ increases in the order of

Li2(3+3=6)=σ1s2,σ*1s2,σ2s2 Bond order =Nb-Na2=4-22=1Li2+(3+3-1=5)=σ1s2,σ*1s2,σ2s1 Bond order =3-22=12=0.5Li2-(3+3+1=7)=σ1s2,σ*1s2,σ2s2σ*2s1 Bond order =4-32=12=0.5 Stability order is Li2>Li2+>Li2-(because Li2- has more number of electrons in antibonding orbitals which destabilises the species).