Stability of the species Li 2 , Li 2 - and Li 2 + increases in the order of

Stability of the species  Li 2 , Li 2 - and Li 2 +  increases in the order of
  1. Li 2 < Li 2 - < Li 2 +
  2. Li 2 - < Li 2 < Li 2 +
  3. Li 2 < Li 2 + < Li 2 -
  4. Li 2 - < Li 2 + < Li 2

Solution

 Li 2 - < Li 2 + < Li 2
Bond order ∝ stability of species
Li2=σ1s2<σ*1s2<σ2s2                      ;  B.O=4−22=1
Li2−=σ1s2<σ*1s2<σ2s2<σ*2s1                      ;  B.O=4−32=0.5
Li2+=σ1s2<σ*1s2<σ2s1                      ;  B.O=3−22=0.5
Li2+ and Li2- both have same bond order, but Li2- has more number of electron in anti-bonding molecular orbitals (experience more inter electronic repulsion) and hence least stable among three species.

Asked in: JEE Main 2013 (07 Apr)

Practice more Chemical Bonding and Molecular Structure questions on Aicharya