Question

Stability of the species $Li_2 , Li_2^- , \, \, and \, \, Li_2^+$ increases in the order of

• A. $Li < Li_2^+ < Li_2^-$
• B. $Li_2^- < Li_2^+ < Li_2$
• C. $Li_2 < Li_2^- < Li_2^+$
• D. $Li_2^- < Li_2 < Li_2^+$

Answer 1

Answer: (B)

$Li_2^- < Li_2^+ < Li_2$

Answer 2

The correct answer is B:$Li^-_2< Li^+_2 < Li_2$
Electrons in $Li_2=6$
Bond order$= \frac{4-2}{2} =1$
Electrons for $Li^+_2\space is\space 5$
Bond order$= \frac{3-2}{2} = 0.5$
Electrons for $Li^-_2 \space{is}\space 7$
Bond order$= \frac{4-3}{2} =0.5$
More the electrons in the bonding orbitals the more is the stability.
Therefore, the order of stability is $Li^-_2< Li^+_2 < Li_2$