Answer:
C2^2+ will or will not exist?
Because of sp mixing Ď3> Ď€1; assume Ď*2 antibonding that is not always the case (can be approximately nonbonding):
C2^2+ = 6e- Ď1(2e-) Ď*2 (2e-) Ď€1(2e-) Ď3(0e-) Ď€2*(0e-) Ď4(0e-) *
Bond Order (bo) = [ÎŁ (bonding e-) - ÎŁ (antibonding e-)]/2
= [4 (Ď1(2e-)Ď€1(2e-)) -2 (Ď*2 (2e-))] = 1
So it is bonding and predicted to exist.
b. Li2 will or will not exist?
(cf H2!) Li2 = 2e Ď1(2e-) Ď*2 (0e-) bo = 1; should (and does) exist
c. Be2^2+ will or will not exist?
Be2^2+ = 2e Ď1(2e-) Ď*2 (0e-) bo = 1; should exist
d. Li2^2- will or will not exist?
Li2^2- 4e- Ď1(2e-) Ď*2 (2e-) bo = 0; will not exist